(b) Rs 50
Let the C.P. of the pair of sunglasses be Rs x
Then S.P. = \(\frac{X\times 125}{100}\) = Rs \(\frac{5X}{4}\)
New C.P. = Rs \(\big(\frac{75}{100}\times X\big)\) = Rs \(\frac{3X}{4}\)
New S.P. = Rs \(\big(\frac{5X}{4}-10\big)\)
Given, \(\frac{5X}{4}\) - 10 = \(\frac{140}{100}\) x \(\frac{3X}{4}\) \(\Rightarrow\) \(\frac{5X}{4}\) - \(\frac{21X}{20}\) = 10
\(\Rightarrow\) \(\frac{25X-21X}{20}\) = 10
\(\Rightarrow\) 4x = 200
\(\Rightarrow\) x = Rs 50.