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Previous Year Questions
If a and b are non-negative real numbers such that a+2b=6, then the average of the maximum and minimum possible values of (a+b) is
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Explanatory Answer
a + 2b = 6
a + b = 6 - b
Clearly, the maximum/minimum value of (a + b) depends on the value of b.
Since a and b are positive real numbers,
The minimum value that b can take is 0.
The maximum value that b can take is when a is 0.
0 + 2b = 6
b = 3.
When b = 0; a + b = 6 - b = 6
When b = 3; a + b = 6 - 3 = 3
Therefore, the minimum and maximum values of (a + b) are 3 and 6 respectively.
The average of these extreme values is ( 3 + 6)/2
Regular polygons A and B have number of sides in the ratio 1 : 2 and interior angles in the ratio 3 : 4. Then the number of sides of B equals
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Working alone, the times taken by Anu, Tanu and Manu to complete any job are in the ratio 5 : 8 : 10. They accept a job which they can finish in 4 days if they all work together for 8 hours per day. However, Anu and Tanu work together for the first 6 days, working 6 hours 40 minutes per day. Then, the number of hours that Manu will take to complete the remaining job working alone is
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Explanatory Answer
Time taken by Anu, Tanu and Manu to complete a job is in the ratio 5 : 8 : 10
This means that their efficiencies are in the ratio 15 : 18 : 110
Or, their efficiencies are in the ratios 8 : 5 : 4
This means, for instance, if Anu can wash 8 plates in an hour, Tanu and Manu can wash 5 & 4
plates respectively in one hour.
So, let us remodel the entire question over this imaginary scenario of washing plates…
All three of them finish the job in 4 days working 8 hours per day.
Anu, Tanu and Manu can wash 8, 5 and 4 plates respectively in an hour.
So the total number of plates = (8+5+4)×4×8=17×4×8
Anu and Tanu work together for 6 days, working 6 hours 40 minutes per day.
The total number of plates washed by them = (8+5)×6×623=13×40
So the remaining plates to be washed =17×4×8−13×40
=4(17×8−130)
=4(80+56−130)
=4×6
So, the question is, in how many hours can Manu wash 4×6 plates?
We know that Manu can wash 4 plates in one hour.
Therefore, he requires 6 hours to wash 4×6 plates.
The price of a precious stone is directly proportional to the square of its weight. Sita has a precious stone weighing 18 units. If she breaks it into four pieces with each piece having distinct integer weight, then the difference between the highest and lowest possible values of the total price of the four pieces will be 288000. Then, the price of the original precious stone is
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Anil borrows Rs 2 lakhs at an interest rate of 8% per annum, compounded half-yearly. He repays Rs 10320 at the end of the first year and closes the loan by paying the outstanding amount at the end of the third year. Then, the total interest, in rupees, paid over the three years is nearest to
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Ravi is driving at a speed of 40 km/h on a road. Vijay is 54 meters behind Ravi and driving in the same direction as Ravi. Ashok is driving along the same road from the opposite direction at a speed of 50 km/h and is 225 meters away from Ravi. The speed, in km/h, at which Vijay should drive so that all the three cross each other at the same time, is
Video Explanation

Explanatory Answer
The speeds of Ravi and Ashok converted to meters per second are 40×5/18=100/9 m/s and 50×5/18=1259 m/s50×518=125/9 m/s respectively.
The relative speed between Ravi and Ashok = 100/9+125/9=225/9 m/s
So they meet exactly after 225/225/9=9 seconds.The distance covered by R in 9 seconds = 100/9×9=100 m.
So, for all three of them to meet at the same time Vijay has to cover 54 + 100 = 154m in 9
Seconds.
∴ The speed of Vijay = 154/9 m/s=154/9×185=61.6kmph
Pipes A and C are fill pipes while Pipe B is a drain pipe of a tank. Pipe B empties the full tank in one hour less than the time taken by Pipe A to fill the empty tank. When pipes A, B and C are turned on together, the empty tank is filled in two hours. If pipes B and C are turned on together when the tank is empty and Pipe B is turned off after one hour, then Pipe C takes another one hour and 15 minutes to fill the remaining tank. If Pipe A can fill the empty tank in less than five hours, then the time taken, in minutes, by Pipe C to fill the empty tank is
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Explanatory Answer
Let the time taken by A to fill the tank alone be x hr, which implies the time taken by B to empty the tank alone is (x-1)hr B is the drainage pipe, and the time taken by C to fill the tank is y hours
It is given that when pipe A,B and C are turned on together, the empty tank is filled in two hours. Hence, 1/x- 1/x-1 +1/y= 1/2
It is given that if pipes B and C are turned on together when the tank is empty and pipe B is turned off after one hour, then pipe C takes another one hour and 15 min to fill the remaining tank
Hence, B worked for 1hr, and C worked for 2hr 15min, which is equal to 9/4hours
In 1 hour, B worked -1/x-1 units, and in 9/4 hours, C worked 9/4y units. Hence, 9/4y-1/x-1=1
Solving both the equations we get y=3/2 and x=3. Hence, the time taken by C is 3/2 hr which is equal to 90 Min
Minu purchases a pair of sunglasses at Rs.1000 and sells to Kanu at 20% profit. Then, Kanu sells it back to Minu at 20% loss. Finally, Minu sells the same pair of sunglasses to Tanu. If the total profit made by Minu from all her transactions is Rs.500, then the percentage of profit made by Minu when she sold the pair of sunglasses to Tanu is
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Explanatory Answer
“Minu purchases a pair of sunglasses at Rs.1000 and sells to Kanu at 20% profit.”
This means, Minu purchased the glasses at Rs.1000 and sold them to Kanu at Rs.1200.
Minu made a profit of Rs. 200 so far.
“Then, Kanu sells it back to Minu at 20% loss.”
This means, Kanu sold the glasses back to Minu at 80% of 1200 = Rs. 960
“Finally, Minu sells the same pair of sunglasses to Tanu the total profit made by Minu from all her transactions is Rs.500”
This means, Minu has to make a further profit of Rs. 300. She achieves this by selling the glasses back to Tanu at 960 + 300 = Rs.1260
So the profit % in the transaction is 300/960×100=31.25%
In a company, 20% of the employees work in the manufacturing department. If the total salary obtained by all the manufacturing employees is one-sixth of the total salary obtained by all the employees in the company, then the ratio of the average salary obtained by the manufacturing employees to the average salary obtained by the non-manufacturing employees is
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Explanatory Answer
In a company, 20% of the employees work in the manufacturing department.” The ratio of number of manufacturing to non-manufacturing employees = 1: 4
So, let the number of manufacturing to non-manufacturing employees be x and 4x respectively. “the total salary obtained by all the manufacturing employees is one-sixth of the total salary obtained by all the employees in the company,” Ratio of total salaries of manufacturing to non-manufacturing employees = 1: 5
So, let the total salaries of manufacturing to non-manufacturing employees be y and 5y respectively.
So, the ratio of average salaries of manufacturing to non-manufacturing employees will be y/x:5y/ 4x=4:5
The number of positive integers less than 50, having exactly two distinct factors other than 1 and itself, is
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Explanatory Answer
A positive integer less than 50, having exactly two distinct factors other than 1 and itself, is either a perfect cube below 50 or an integer that is a product of exactly two distinct primes.
Case i)
Perfect cubes below 50 are 23 and 33. So, two numbers here
Case ii)
For the product of two primes to be below 50, the individual primes should be below 25.
(Because, the smallest prime is 2 and multiplying 2 with anything greater than or equal to 25 yields a number greater than or equal to 50.)
2, 3, 5, 7, 11, 13, 17, 19, 23 are prime numbers less than 25.
2, 3, 5, 7 are the primes less than √50, any product of two numbers among them yields a product less than 50.
11, 13, 17, 19, 23 are the primes greater than √50, any product of two numbers among them yields a product greater than 50.
So, there are 0 pairs here.
Between the two lists 11 and 13 can pair with 2 and 3, while 17, 19, and 23 can only pair with 2.
So, there are 7 pairs here.
So, totally, there are 2 + 6 + 0 + 7 = 15 such numbers.
For any natural numbers m,n, and k, such that k divides both m+2n and 3m+4n,k must be a common divisor of
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Explanatory Answer
k divides m + 2n
So, k also divides 2(m + 2n) = 2m + 4n
It is given that k divides 3m + 4n
Which means, k should also divide (3m + 4n) – (2m + 4n)
∴k divides m
Since k divides m and m + 2n
k should also divide (m + 2n) – m = 2n
Therefore, k divides m and 2n.
In a regular polygon, any interior angle exceeds the exterior angle by 120 degrees. Then, the number of diagonals of this polygon is
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A rectangle with the largest possible area is drawn inside a semicircle of radius 2cm . Then, the ratio of the lengths of the largest to the smallest side of this rectangle is
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Gautam and Suhani, working together, can finish a job in 20 days. If Gautam does only 60% of his usual work on a day, Suhani must do 150% of her usual work on that day to exactly make up for it. Then, the number of days required by the faster worker to complete the job working alone is
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The number of coins collected per week by two coin-collectors A and B are in the ratio 3 : 4. If the total number of coins collected by A in 5 weeks is a multiple of 7, and the total number of coins collected by B in 3 weeks is a multiple of 24, then the minimum possible number of coins collected by A in one week is
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Explanatory Answer
Let the number of coins collected by A and B in one week be 3x and 4x respectfully.
The total number of coins collected by A in 5 weeks = 15x
For 15x to be a multiple of 7, x has to be a multiple of 7.
The total number of coins collected by B in 3 weeks = 12x
For 12x to be a multiple of 24, x has to be a multiple of 2.
Therefore, x has to be a multiple of 7 × 2 = 14
The minimum value that x can take is 14.
So, the minimum coins collected by A in one week = 3x = 3 × 14 = 42.
A fruit seller has a stock of mangoes, bananas and apples with at least one fruit of each type. At the beginning of a day, the number of mangoes make up 40% of his stock. That day, he sells half of the mangoes, 96 bananas and 40% of the apples. At the end of the day, he ends up selling 50% of the fruits. The smallest possible total number of fruits in the stock at the beginning of the day is
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A boat takes 2 hours to travel downstream a river from port A to port B, and 3 hours to return to port A. Another boat takes a total of 6 hours to travel from port B to port A and return to port B. If the speeds of the boats and the river are constant, then the time, in hours, taken by the slower boat to travel from port A to port B is
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There are three persons A, B and C in a room. If a person D joins the room, the average weight of the persons in the room reduces by x kg. Instead of D, if person E joins the room, the average weight of the persons in the room increases by 2x kg. If the weight of E is 12 kg more than that of D, then the value of x is
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A merchant purchases a cloth at a rate of Rs.100 per meter and receives 5 cm length of cloth free for every 100 cm length of cloth purchased by him. He sells the same cloth at a rate of Rs.110 per meter but cheats his customers by giving 95 cm length of cloth for every 100 cm length of cloth purchased by the customers. If the merchant provides a 5% discount, the resulting profit earned by him is
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The population of a town in 2020 was 100000. The population decreased by y% from the year 2020 to 2021, and increased by x% from the year 2021 to 2022, where x and y are two natural numbers. If population in 2022 was greater than the population in 2020 and the difference between x and y is 10, then the lowest possible population of the town in 2021 was
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Anil mixes cocoa with sugar in the ratio 3 : 2 to prepare mixture A, and coffee with sugar in the ratio 7 : 3 to prepare mixture B. He combines mixtures A and B in the ratio 2 : 3 to make a new mixture C. If he mixes C with an equal amount of milk to make a drink, then the percentage of sugar in this drink will be
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Explanatory Answer
Mixture A and B are mixed in the ratio 2 : 3 to produce mixture C.
Let us assume that 20 kgs of mixture A is mixed with 30 kgs of mixture B to produce 50 kgs of mixture C.
Mixture A has cocoa and sugar in the ratio 3 : 2. This means, 20 kgs of mixture A contains 12 kgs of cocoa and 8 kgs of sugar. Mixture B has coffee and sugar in the ratio 7 : 3. This means, 30 kgs of mixture B contains 21 kgs of coffee and 9 kgs of sugar.
So, totally, 50kgs of mixture C has 17 kgs of sugar.
50 kgs of mixture C is mixed with 50 kgs of milk.
So, the percentage of sugar in the entire mixture =17/100×100=17%
Rahul, Rakshita and Gurmeet, working together, would have taken more than 7 days to finish a job. On the other hand, Rahul and Gurmeet, working together would have taken less than 15 days to finish the job. However, they all worked together for 6 days, followed by Rakshita, who worked alone for 3 more days to finish the job. If Rakshita had worked alone on the job then the number of days she would have taken to finish the job, cannot be
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The sum of the first two natural numbers, each having 15 factors (including 1 and the number itself), is
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Let nn and mm be two positive integers such that there are exactly 41 integers greater than 8m8m and less than 8n8n, which can be expressed as powers of 2. Then, the smallest possible value of n +mn + m is
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We need to have 41 integers that can be expressed as powers of 2 between 8m and 8n.
That is we need to have 41 integers that can be expressed as powers of 2 between 23m and 23n.
The numbers will be of the form: 23m,23n+1,23m+2,23m+3,…,23m+41,23n
clearly, 3n−1=3m+41
3(n−m)=42
n−m=14
The smallest value m
can take =1
, then n=15
m+n=1+15=16
A quadrilateral ABCD is inscribed in a circle such that AB : CD = 2 : 1 and BC : AD = 5 : 4. If AC and BD intersect at the point E, then AE : CE equals
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The amount of job that Amal, Sunil and Kamal can individually do in a day, are in harmonic progression. Kamal takes twice as much time as Amal to do the same amount of job. If Amal and Sunil work for 4 days and 9 days, respectively, Kamal needs to work for 16 days to finish the remaining job. Then the number of days Sunil will take to finish the job working alone, is
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In an examination, the average marks of 4 girls and 6 boys is 24. Each of the girls has the same marks while each of the boys has the same marks. If the marks of any girl is at most double the marks of any boy, but not less than the marks of any boy, then the number of possible distinct integer values of the total marks of 2 girls and 6 boys is
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The salaries of three friends Sita, Gita and Mita are initially in the ratio 5 : 6 : 7, respectively. In the first year, they get salary hikes of 20%, 25% and 20%, respectively. In the second year, Sita and Mita get salary hikes of 40% and 25%, respectively, and the salary of Gita becomes equal to the mean salary of the three friends. The salary hike of Gita in the second year is
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Let n be the least positive integer such that 168 is a factor of 1134n . If m is the least positive integer such that 1134n is a factor of 168m , then n+nm+m equals
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A lab experiment measures the number of organisms at 8 am every day. Starting with 2 organisms on the first day, the number of organisms on any day is equal to 3 more than twice the number on the previous day. If the number of organisms on the nth day exceeds one million, then the lowest possible value of n is
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Arvind travels from town A to town B, and Surbhi from town B to town A, both starting at the same time along the same route. After meeting each other, Arvind takes 6 hours to reach town B while Surbhi takes 24 hours to reach town A. If Arvind travelled at a speed of 54 km/h, then the distance, in km, between town A and town B is
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