Please submit your concern

Question:

A change making machine contains 1 rupee, 2 rupee and 5 rupee coins. The total number of coins is 300. The amount is Rs. 960. If the number of 1 rupee coins and the number of 2 rupee coins are interchanged, the value comes down by Rs. 40. The total number of 5 rupee coins is

Explanation:

Let the number of Re. 1, Re. 2 and Re. 5 coins be x, y and z respectively.

x + y + z = 300                           ...(i)

x + 2y + 5z = 960                       ...(ii)

2x + y + 5z = 920                       ...(iii)

Adding equation (ii) and equation (iii), we get,

3x + 3y + 10z = 1880                 ...(iv)

Multiply equation (i) by 3, we get,

3x + 3y + 3z = 900                     ...(v)

Subtracting equation (v) from equation (iv), we get,

7z = 980

∴ z = 140

Hence, option (b).