Find profit or loss per cent when the cost price is Rs. 350 and the selling price is Rs. 420.

Given: CP = Rs. 350

SP = Rs. 420

profit or loss% = ?

Here, SP > CP. So, there will be profit in this case.

By using the formula,

$\mathrm{Profit}\%=\frac{\mathrm{SP}-\mathrm{CP}}{\mathrm{CP}}\times 100$

$=\frac{420-350}{350}\times 100$

$=\frac{70}{350}\times 100$

$=\frac{1}{5}\times 100$

$=20\%$

Hence, the profit percentage is 20%.