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A trader allows a discount of 20% on his goods and still makes a profit of 25%.Find the profit percent made, if he sells his goods at: (1) the Marker price (2) at 10% discount

What i've tried:

let MP = 100
D=20%
=> SP = 80

SP = 80
P = 25%

SP      CP
125     100
80       ?

CP = (80 * 100)/125
   = 64

profit = SP - CP 
       = 80 - 64
       = 16

P% = 16/64 * 100  
   = 25%  

but the correct answer is 56.25 %

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Is this an Icse board question? Cause copper hat's method is not allowed for board. –  user1659754 Sep 30 '12 at 7:54
    
Yes it is. By the way- don't post queries as answers, use comments for those sorts of things. –  Ghost Sep 30 '12 at 8:23
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1 Answer

up vote 0 down vote accepted

Let $S$ be the usual sale price, $C$ be the cost.

You are given that $\frac{0.8 S } { C} = 1.25$.

For (1), you want to compute $\frac{S } { C} = \frac{1} {0.8} \frac{0.8 S } { C} = \frac{1} { 0.8} 1.25 = 1.5625$ (ie, 56.25%).

For (2), you want to compute $\frac{0.9 S } { C} = 0.9 \cdot 1.5625 = 1.40625$ (ie, 40.625%).

share|improve this answer
    
i didn't understand the 3rd line, why's it 1/0.8 ? –  Ghost Aug 31 '12 at 5:10
    
Divide both sides of the equation on Line 2 by 0.8. (A 20% reduction corresponds to a sales price of $0.8S$.) –  copper.hat Aug 31 '12 at 5:47
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