Question

The price of coal rises by 25%. If a family wants to keep its expense for coal same, by what per cent should it decrease its coal consumption ? ​

Answer 1

CP of coal = Rs x per kg

Quantity of coal consumed = m kg

Expenditure on coal = Rs mx

Increased CP of coal = Rs 1•2x

Increased over head expenditure = Rs 1•2mx

Let the reduced consumption of coal = m1 kg

Such that 1•2m1x = Mx

Or m1 = m/1•2

Reduction in consumption = m - m1 = 0•2m/1•2

Percentage reduction = 2/12*100 = 50/3 = 16•67%