If the price of onion increases from Rs. 15 per kg to Rs .50 per kg , then by what percentage a household should decrease the consumption of onion so that expenditure remains same?

Correct option is A

​Solution:​

Let the household consume a kg of onion earlier and b kgs later.

The amount paid by the household earlier = Rs.15a

The amount paid by the household later = Rs.50b

Since both prices should be the same

=> 15a = 50b

=> 3a = 10b

=> b = $$\frac{3a}{10}$$​

Required percent = $$\frac{(a -b)}{a}× 100\$$​

​$$= \frac{(a - \frac{3a}{10})}a × 100 \\\ \\= \frac{7}{10}\times 100 \\\ \\= 70$$​​

The required percentage to decrease the consumption is 70 percent.