In the expression xy2, the value of both variables x and y are decreased by 20%. By this, the value of the expression is decreased by?
Answer & explanation
Correct answer: option 3
xy2 = x × y × y
= [ 1 - \(\frac{20}{100}\)] × [ 1 - \(\frac{20}{100}\)] × [ 1 - \(\frac{20}{100}\)]
= \(\frac{80}{100}\) × \(\frac{80}{100}\) × \(\frac{80}{100}\)
= \(\frac{8}{10}\) × \(\frac{8}{10}\) × \(\frac{8}{10}\) = \(\frac{512}{1000}\)
Let original value of xy2 is 1000 , hence decreased value = 1000-512 = 488
⇒ Decreased percentage = \(\frac{488}{1000}\) × 100 = 48.8%