Krishna bought a camera and paid 20% less than its original price. He sold it at 40% profit on the price he had paid. The percentage of profit earned by Krishna on the original price was:

Krishna bought a camera and paid 20% less than its original price. He sold it at 40% profit on the price he had paid. The percentage of profit earned by Krishna on the original price was:
[A]15%
[B]12%
[C]22%
[D]32%

12%
Let the original price be x Rs.
$= \frac{80}{100}\times x = \frac{4x}{5}Rs.$
$SP = \frac{4x}{5}\times \frac{140}{100} = \frac{28x}{25}Rs.$
Gain on original price =
$\frac{28x}{25} - x = \frac{3x}{25}$
$\therefore Gain \%= \frac{3x}{\frac{25}{x}\times 100} = 12\%$
Hence option [B] is the right answer.