Question

In a piggy bank the total number of coins of Rs. 5 and Rs. 1 is 100. If the total coins amount is 300, then what is the number of coins of each denomination?

(a) 30, 70

(b) 50, 50

(c) 45, 55

(d) 60, 40

The question was asked in an internship interview.

This intriguing question originated from Solution of Two Linear Equations in Two Variables in Different Methods topic in section Pair of Linear Equations in Two Variables of Mathematics – Class 10

Answer 1

Right choice is (b) 50, 50

For explanation I would say: Let the coins of Rs. 5 be x and that of Rs. 1 be y

Total number of coins is 100

x+y=100

y=100-x

Total amount of coins is 300

Also, 5x+y=300     (1)

Substituting y=100-x in equation (1) we get,

5x+100-x=300

4x=200

x=50

y=100-x=100-50=50

The coins of each denomination are 50.