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Hello sir, Can you please explain this question

Rajiv is a student in a business school. After every test he calculates his cumulative average. QT and OB were his last two tests. 83 marks in QT increased his average by 2. 75 marks in OB further increased his average by 1. Reasoning is the next test, if he gets 51 in Reasoning, his average will be _____?

  1. 63
  2. 62
  3. 61
  4. 60

Hello Ritika, 

Find the solution.........

Let initial average =a and number of subjects = n

According to first condition,

an + 83 = (n+1) (a + 2)

an + 83 = an + 2n + a + 2

a + 2n = 81…………………1)

According to second condition,

{(a + 2) (n + 1)+ 75} = (a+2+1)(n+2)

an + a +2n + 2 + 75 = an + 2a + 3n + 6

a + n =71 …………………………..2)

From eq. 1) and 2)

n = 10 and x = 61

After paper OT and OB

Average = 61 + 2 + 1 =64

Number of subjects = 10 + 1 + 1 =12

So after getting 51 in reasoning,

Average = (64 x 12 + 51)/(13) =819/13=63

17 Answers

In a house ABC with 12 members, the avg age of the members was 42 years in the year 1966. The next year, the oldest member of the family died at the age of 66 and a member decided to shift to other locality. After 1 year a baby was born and in the same year another member left the house who is 3 years younger to the member who had left the house the previous year. After 2 more years, the average age of all the members was 44 years. What was the age of the member who had left the house when the oldest member died?

A. 20 B.21 C. 41 D.42

This post was modified 2 years ago by Gaurav Jain

A few students decided to buy a gift for their teacher. So, each of them decided to contribute an equal amount for the gift. But when they went to buy the gift, they found that the price of it had increased by 16.66%. Now 2 more students joined to contribute and because of this the cost per head decreased by Re 1. If the contribution per head is an integer, which of the following cant be the initial number of students who had decided to contribute for the gift?

A. 5    B.6    C. 7    D.8

initial contribution p , and number = n , so initial price = pn 

and final price = 7/6pn

final contri = p-1 and number of students = n+2

so 7/6pn = (p-1) (n+2)

from this n = (12p-12)/(p+6)

now n=7 won't be possible


In the island of Hoola Boola Moola , inhabitants have a strang process of calculating their average incomes and expenditures. According to an old legend prevalent on that island. the average monthly income had to be calculated on the basis of 14 months in a calendar year while the average monthly expenditure was to be calculated on the basis of 9months per year. This would lead to people having an underestimation of their saving since there would be an underestimation of the income and overestimation of their expenditure per month.


Q.Mr. Boogie Woogle comes back from the USSR and convinces his community comprising 273 families to start calculating the average incomeon on the basis of 12 months per calendar year.Now if it is knon that the average estimated income in his community is(according to the old system) 87 Moolahs per month. Then what will be the change in the average estimated savings for the island of Hoola Boola Moola. (Assume that there is no other change).

 1) 251.60 Moolahs 

2) 282.75 Moolahs

 3) 312.75 Moolahs

 4) Cannot Be Determined


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