Question

Rahul saxena gets 20% profit on sale of 20 items in a rupee.what is the profit/loss in percent when he sales 25 item in a rupee???

Answer 1

Rahul selled 20 items in 1 rupee or 100 paise.
So, SP of 1 item = 100/20 = 5 paise
Profit = 20%
Hence, CP + CP×$\frac{20}{100}$ = SP
=> CP + CP×$\frac{1}{5}$ = 5
=> $\frac{6}{5}$CP = 5
=> CP = $\frac{25}{6}$ paise

If he sells 25 items in a rupee, then 
newSP of 1 item = 100/25 = 4 paise

Since, newSP is less than CP, so here Raghav will have loss
Loss = CP -SP
        = $\frac{25}{6}$ - 4 =$\frac{25-24}{6}$
        = $\frac{1}{6}$ paise
Hence, Loss% = $\frac{Loss}{CP}$×100
                        = $\frac{1/6}{25/6}$ × 100
                        = 4%

There will be loss of 4% if Rahul sells 25 items in a rupee.