A merchant has announced 25% rebate on prices of ready made garments at the time of sale. If a purchaser needs to have a rebate of ? 400, then how many shirts, each costing ? 320, should he purchase?

Let the marked price of item = ? N
? {(100 - 14) /100 } of N = 645
? N = (645 x 100)/86 = ? 750

Here, r₁ = 10 %, r₂ = 20% and r₃ = 30%
? Required discount
= [1 - (1 - r₁/100) (1 - r₂/100) (1 - r₃/100)] x 100%
= [1 - (1 -10/100) (1 - 20/100) (1 - 30/100)] x 100%
= {1 - (9/10) x (4/5) x (7/10)} x 100%
= (1 - 0.504) x 100% = 49.6%

Let amount of electricity bill = ? N
? 4% of N = 13
? (4 x N)/100 = 13
? N = 13 x 25 = ? 325

Let the original price of be N .
? At discount of 20% article costs ? 596
? 596 = (80 x N)/100
? N = (596 x 100)/80
? N = 745
? original price = ? 745

Given, r₁ = 20% and r₂ = 20%
? Single discount equal to r₁ and r₂
= (r₁ + r₂ - r₁ x r₂) / 100 %
= (20 + 20 - 20 x 20) / 100
= 40 - 4 = 36%

? Single discount equivalent to 36% and 4%
= 36 + 4 - {(36 x 4)/100} = 38.56

? Required difference
= {(40 - 38.56) x 500}/100 = 1.44 x 5 = ? 7.20

Here, r = 20% and r₁ = 15%
Required profit per cent =[ r(100 - r₁)/100] - r₁
= [20(100 - 15)/100] - 15
= 17 - 15
= 2%

Let labelled price of TV = ? R
? SP of the TV = [R x (100 - 20)] / 100 = ? 4R/5
But 16800 - 800 = 4R/5
? x = (16000 x 5)/4 = ? 20000

? Marked price of an article = ? 500
The selling price of article after discount 20% and 10%
= 500 x {(100 - 20) / 100} x {(100 - 10) / 100}
= 500 x (80/100) x (90/100)
= ? 360

Here, r₁ = 20% and r₂ = 5%
? Required percentage
= r₁ + r₂ - (r₁ x r₂)/100%
= 20 + 5 - (20 x 5)/100
= 25 - 1
=24%