Question

Average marks scored by three friends A, B and C in an exam is 80. If marks scored by A is 25% more than B and difference of marks scored by B and C is 20 (B score more than C). How much did A score?
1. 100
2. 80
3. 90
4. 60

Answer 1

Correct Answer - Option 1 : 100

Given:

Average marks of A, B and C = 80

Marks scored by A = B + 25% of B

Marks scored by B – marks scored by C = 20

Formula used:

Average = Total sum / Total number

Total sum = Average × Total number

Calculation:

Total marks scored by (A + B + C) = 3 × 80 = 240

Let, B scored = x

A scored = x + 25% of x = x + x / 4 = 5x / 4

Now, marks scored by C = x – 20

Total marks scored by A + B + C = 5x / 4 + x + (x – 20) = 1.25x + x + x – 20 = 3.25x – 20

⇒ 3.25x – 20 = 240

⇒ 3.25x = 240 + 20 = 260

⇒ x = 260 / 3.25 = 80

∴ , marks scored by A = 80 + 25% of 80 = 100