The marked price of a watch is 800. A shopkeeper gives

The marked price of a watch is 800. A shopkeeper gives two successive discounts and sells the watch at 612. If the first discount is 10%, the second discount is :

Let the second discount be D₂ %.
Then, 90 % of (100 – D₂) % of 800 = 612

⇒	90	×	100 − D₂	× 800 = 612
	100		100

⇒ 100 − D₂ =	612 × 100	= 85
	90 × 8

⇒ D₂ = 100 – 85 = 15%
Another method to solve :
Here, M.P. = Rs. 800, S.P. = Rs. 612, D₁ = 10%, D₂ = ?

S.P. = M.P.		100 − D₁			100 − D₂
		100			100

612 = 800 ×		100 − 10			100 − D₂
		100			100

612 = 800 ×	90	×	100 − D₂
	100		100

6120	= 100 × D₂
72

D₂ =	100 − 6120
	72

D₂ =	7200 − 6120	= 15%
	72