Petrol price increases by 75%. By what percent should consumption be reduced so that expenditure increases only by 26%?

Correct option is D

Given:

The price of petrol increases by 75%.
The expenditure on petrol increases by 26%.
Formula Used:
Expenditure = Price × Consumption
Solution:
Let the original price of petrol be  P and the original consumption be  C.
Original expenditure =$$P \times C .$$​
After the price increase:
New price = P + 0.75P = 1.75P 
Let the new consumption be C' .
New expenditure =$$1.75P \times C'.$$​
New expenditure = Original expenditure + 47% of original expenditure
​$$1.75P \times C' = 1.26\times (P \times C) .$$​​
C' =$$0.72 \times C$$​ 
Reduction = C - C' = C - 0.72C = 0.28C .
Percentage reduction =$$\frac{0.28 C}{C} \times 100\% = 28\%$$

Alternate Method:

The price of petrol increases by 75%.

Then, 100 + 75 = 175

The expenditure on petrol increases by 47%.

100 + 26 = 126

So, Reduction= 175 - 126 = 49

Percentage reduction =$$\frac{49}{175}\times 100 = 28\%$$