Q. The marked price of a watch was Rs. 720/-. A man bought the same for Rs. 550.80, after getting two successive discount, the first art 10%. What was the second discount rate?
Answer: 15%
Notes: Marked price = Rs. 720 Actual price = Rs. 550.80 First discount = 10% Let the second discount be x% Then, we can write 720(1 - 0.10)(1 - 0.01x) = 550.80 $latex =>$720 $latex \times$ 0.9(1 - 0.01x) = 550.80 $latex =>$648(1 - 0.01x) = 550.80 $latex => 1-0.01x=\frac{550.8}{648}&s=1$ $latex =>0.01x=1-\frac{550.8}{648}&s=1$ $latex =>x=\frac{1-0.85}{0.01}&s=1$ $latex =>x=0.15\times 100$ $latex =>x=15$ Hence option [B] is the right answer.

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