1.  A total of 324 coins of 20 paise and 25 paise make a sum of Rs. 71. The number of 25-paise coins is

A. 120
B. 124
C. 144
D. 200

Answer: Option B

Explanation:

Let the number of 20-paise coins be x. Then, number of 25-paise coins = (324 - x).

Therefore 0.20 x x + 0.25 (324 - x) = 71 20x + 25 (324 - x) = 7100

5x= 1000 x = 200. Hence, number of 25-paise coins = (324 - x) - 124.