Question

find the single discount equivalent to two successive discount of 10% and 20%

Answer 1

Use Formula,
Equivalent Discount = (A + B) - (AB/100) where A = First Discount, B =Second Discount.
Equivalent Discount = (20 + 10) - (20*10)/100
Equivalent Discount = 30 - 2 = 28%.

Graphic Change Method
100==20%(disc.)==>80==10%(disc.)==>72
Equivalent discount = 28%.