DRDO Multi tasking staff Model paper 5

Total amount = Rs 130
Ratio of coins respectively for 1, 2 and 5-rupee coins = 10 ∶ 10 ∶ 7
Let the no. of coins be 10x, 10x and 7x
⇒ Total amount by 1-rupee coins = 1 × 10x = 10x ----(1)
⇒ Total amount by 2-rupee coins = 2 × 10x = 20x ----(2)
⇒ Total amount by 5-rupee coins = 5 × (7x) = 35x ----(3)
⇒ 10x + 20x + 35x = 130 (From (1), (2) and (3)) ----(4)
⇒ 65x = 130
⇒ x = 130/65 = 2
No. of 1-rupee coins = 10x = 10 × 2 = 20
No. of 2-rupee coins = 10x = 10 × 2 = 20
No. of 5-rupee coins = 7x = 7 × 2 = 14
∴ Total no. of 2-rupee coins = 20.