Question

The price of a commodity increases by 20%. What price should a housewife pay for it now if it costed her 150 rs earlier ​

Answer 1

Let the price of commodity be 100 Rs.
Suppose a man buys 7 commodities per month.
Total expenditure= 100*7=700.

Increased price = 140*100/100=140.
In order to keep expenditure constant, he has to buy 700/140 = 5 commodities per month.
Decrease in purchase =
2 commodities
% decrease= 2*100/7=200/7 %
= 28.57 % (approximately)

Second way -
Let a man buy y commodities for x Rs.
Total expenditure= Rs. xy
Increased price of commodity=140x/100=7x/5
= 1.4x Rs.
So, in order to keep expenditure constant, man has to buy
xy/1.4x=5y/7 commodities.
Decrease in purchase=
y-5y/7= 2y/7 commodities
% decrease= 2y*100/7y
= 200/7 % = 28.57 %(approx.)