# A Consumer Spends Rs 400 on a Good Priced at Rs 4 per Unit. When the Price Rises by 25 Percent, the Consumer Continues to Spend Rs 400. Calculate the Price Elasticity of Demand by Percentage Method. - Economics

A consumer spends Rs 400 on a good priced at Rs 4 per unit. When the price rises by 25 percent, the consumer continues to spend Rs 400. Calculate the price elasticity of demand by percentage method.

#### Solution

Given:
$\text{ Initial Total Expenditure }\left( T E_0 \right) = Rs 400$
$\text{ Final Total Expenditure }\left( T E_1 \right) = Rs 400$
$\text{ Initial Price }\left( P_0 \right) = Rs 4$
$\text{ Percentage change in price }= + 25$
$\text{ Percentage change in price }= \frac{P_1 - P_0}{P_0} \times 100$
$25 = \frac{P_1 - 4}{4} \times 100$
$\frac{100}{100} = P_1 - 4$
$P_1 = 5$

 Price (P) $\text{Total Expenditure }\left( TE \right) =\text{ Price }\left( P \right) \times \text{ Quantity }\left( Q \right)$ $\text{ Quantity }\left( Q \right) = \frac{TE}{P}$+ P0 = Rs 4 TE0 = Rs 400 Q0 = 100 P1= Rs 5 TE1 = Rs 400 Q1 = 80

Now,
$E_d = \left( - \right)\frac{\text{ Percentage change in quantity demanded }}{\text{ Percentage change in price }}$
$E_d = \left( - \right)\frac{\frac{Q_1 - Q_0}{Q_0} \times 100}{25}$
$E_d = \left( - \right)\frac{\frac{80 - 100}{100} \times 100}{25}$
$E_d = \left( - \right)\frac{- 20}{25}$
$E_d = 0 . 8$
$\therefore E_d = 0 . 8$

Thus, the price elasticity of demand is 0.8.
Concept: Elasticity of Demand
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