The Average Price of 10 books is Rs.12 While the Average Price of 8 of GMAT Problem Solving

QuestionThe average price of 10 books is Rs.12 while the average price of 8 of these books is Rs.11.75. Of the remaining two books, if the price of one book is 60% more than the price of the other, what is the price of each of these two books?

  1. Rs.10, Rs.16
  2. Rs.12, Rs.18
  3. Rs.14, Rs.20
  4. Rs.16, Rs.24
  5. Rs.18, Rs.26


Correct Answer: A

Solution and Explanation
Approach Solution 1:

Given:

  • The average price of 10 books is Rs.12
  • The average price of 8 of these books is Rs.11.75.

Condition:

  • Of the remaining two books, the price of one book is 60% more than the price of the other

Find out:

  • The price of each of these two books

Total cost of 10 books = 10*12 = 120.
Total cost of 8 books = 8 * 11.75 = 94
Total cost of the remaining 2 books = 26.

NOTE: the price of one book is 60% more than the price of the other. It can be translated as follows:

Let the price of 1 book is x. Considerin this, other must be 160% of x.
160/100 * x
= 1.6x.

Hence,

x + 1.6x = 26

2.6x = 26

x = 26/2.6

x = 260 / 26.

x = 10.

The cost of a book = 10

cost of the other one = 1.6*10 = 16.

Approach Solution 2:
Given:

  • The average price of 10 books is Rs.12
  • The average price of 8 of these books is Rs.11.75.

Condition:

  • Of the remaining two books, the price of one book is 60% more than the price of the other

Find out:

  • The price of each of these two books

cost of 8 books = 11.75*8 = 94
and 2 books = 120-94 = 26
So as per the problem statement, for 2 books ; x+1.6x= 26
x= 10
and 1.6x = 16

Approach Solution 3:
Total price of the remaining two books = 10 x 12 - 8 x 11.75
                                                             = 120 - 94 = Rs 26
Suppose the price of one book = Rs x
Then, price of the other book = x + 60% of x = 160/100​x= 8x/5
Given, x+8x/5​= 26⇒13x/5​= 26
⇒x= 26*5/13​=Rs10
Therefore, price of the other book = Rs 8×10​/5= Rs16

“The average price of 10 books is Rs.12 while the average price of 8 of”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book "GMAT Official Guide 2018 Quantitative Review".To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. GMAT Quant practice papers improve the mathematical knowledge of the candidates as it represents multiple sorts of quantitative problems.


 

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