A person sold his watch for Rs 144. If the percentage of his profit wa

1.	A person sold his watch for Rs 144. If the percentage of his profit was equal to the cost price, then the watch would have cost him (a) Rs 100 (b) Rs 90 (c) Rs 85 (d) Rs 80
Answer» (d) Rs 80 Let C.P. = Rs x, S.P. = Rs 144, Profit = x% \(\therefore\) x + x% of x = 144 \(\Rightarrow\) x + \(\frac{X}{100}\) x x = 144 \(\Rightarrow\) x²+ 100x - 14400 = 0 \(\Rightarrow\) x² + 180x – 80x – 14400 = 0 \(\Rightarrow\) x (x +180) – 80 (x + 180) = 0 \(\Rightarrow\) (x +180) (x – 80) = 0 \(\Rightarrow\) x = – 180 or 80 Neglecting negative values, x = 80.

A person sold his watch for Rs 144. If the percentage of his profit was equal to the cost price, then the watch would have cost him (a) Rs 100 (b) Rs 90 (c) Rs 85 (d) Rs 80

Answer»

(d) Rs 80

Let C.P. = Rs x, S.P. = Rs 144, Profit = x%

\(\therefore\) x + x% of x = 144

\(\Rightarrow\) x + \(\frac{X}{100}\) x x = 144

\(\Rightarrow\) x²+ 100x - 14400 = 0

\(\Rightarrow\) x² + 180x – 80x – 14400 = 0

\(\Rightarrow\) x (x +180) – 80 (x + 180) = 0

\(\Rightarrow\) (x +180) (x – 80) = 0

\(\Rightarrow\) x = – 180 or 80

Neglecting negative values, x = 80.