Rakesh had money to buy 8 mobile handsets of a specific company. But the retailer offered very good discount on that particular handset. Rakesh could buy 10 mobile handsets with the amount he had. What was the discount the retailer offered?

The correct option is 20%.

To understand why this is the correct answer, let us break down the mathematical steps:

Let the original price of one mobile handset be $x$.
Since Rakesh had enough money to buy 8 handsets at this original price, the total amount of money Rakesh had is:

$\text{Total Money}=8x$

With the discount offered by the retailer, let the new discounted price of one mobile handset be $y$.
Rakesh could now buy 10 mobile handsets with the same total amount of money. Therefore, we can write:

$10y=8x$

Solving for the discounted price $y$ in terms of the original price $x$:

$y=\frac{8x}{10}=0.8x$

The amount of discount offered on each handset is the difference between the original price and the discounted price:

$\text{Discount Amount}=x-y=x-0.8x=0.2x$

To find the discount percentage, we divide the discount amount by the original price and multiply by 100:

$\text{Discount Percentage}=\left(\frac{0.2x}{x}\right)\times 100=0.2\times 100=20\%$

Thus, the retailer offered a discount of 20%.