Question

find the selling price if a fountain pen coasting rs 6.20 is sold at a loss of 10 percentage​

Answer 1

6.20/60*10 will give you answer as 1.033
Then subtract it from the given cost you'll get the answer as 5.167

Answer 2

$s.p = {?} \\ \\ c.p = 6.20 rs\\ \\ loss \: percentage(r) =10\% \\ \\ s.p = \frac{100 - r\%}{100} \times c.p \\ \\ \: \: \: \: \: \: = \frac{100 - 10}{100} \times 6.20 \\ \\ \: \: \: \: \: \: = \frac{90}{100} \times 6.20 \\ \\ \: \: \: \: \: \: = \frac{558}{100} \\ \\ \: \: \: \: \: \: = 5.58$