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?

48.8%

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%