Question

10. On selling a sofa-set for 21600, a dealer gains 8%. For how much did he purchase it?
11. On selling a watch for 11400, a shopkeeper loses 5%. For how much did he purchase it?
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Answer 1

Answer:

$10. \: sp \: of \: sofa \: set = 21600 \\ profit \: on \: sofa \: set = 8\% \\ cp = ( \frac{100}{100 + p} ) \times sp \\ cp = ( \frac{100}{100 + 8} ) \times 21600 \\ cp = \frac{100}{108} \times 21600 \\ cp = 20000$

$11. \: \: sp \: of \: watch = 11400 \\ loss \: on \: watch = 5\% \\ cp = ( \frac{100}{100 - l} ) \times sp \\ cp = ( \frac{100}{100 - 5} ) \times 11400 \\ cp = \frac{100}{95} \times 11400 \\ cp = 12000$