Find a single discount equivalent to a discount series of 10%, 15% and 20%.

Correct option is C

Equivalent discount of x%  and y% =  $$x+ y-\frac{xy}{100}$$

Equivalent discount of 10% and 20% = $$10+ 20-\frac{10×20 }{100} = 10+20-2 = 30-2= 28{\%}$$

Equivalent discount of 28% and 15% = $$28+ 15-\frac{28×15 }{100} = 28+15-4.2 = 38.8{\%}$$​​