The price of sugar is increased by 18%. A person wants to increase the expenditure by 12% only. By what percent, correct to one decimalplace, should he decrease his consumption?

This can be determined by using a simple formula that equates the net change in price, consumption and expenditure.

E= $$x+ y + \frac{xy}{100}$$, where E is the net change in expenditure, x is the net change in consumption and y is the net change in the price of the commodity

Here, the change in expenditure is +12, price is +18 so putting these values in the equation

$$12 = x + 18 + \frac{18x}{100}$$

By solving this, we get,

$$12 = \frac{100x+1800x+18x}{100}$$

$$1200$$ = $$118x+1800$$

$$1200-1800$$ = 118x

-600 = 118x

where x = $$\frac{-600}{118}$$

$$x = - 5.1$$℅ ( - indicates that it needs to be decreased)

Therefore, consumption needs to be decreased by 5.1%