Can You please explain this

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navdeepbajwa: Senior | Next Rank: 100 Posts; Posts: 74; Joined: Sun Aug 02, 2009 9:10 pm; Thanked: 1 times; Followed by:1 members

Can You please explain this

by navdeepbajwa » Mon Oct 19, 2009 11:53 pm

Why the answer is 10% and not 7% I am confused and how question can be rephrased if answer needs to be 7%.What is the difference

Two numbers are less than a third number by 30% and 37 % respectively. How much percent is the second number less than the first?

a) 10 % b) 7 % c) 4 % d) 3 %

Solution: .7 & .63

diff in %= (.7 - .63)/.7 * 100= .07/.7 * 100= 10%

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Source: Beat The GMAT — Problem Solving | Mon Oct 19, 2009 11:53 pm

papgust: Community Manager; Posts: 1537; Joined: Mon Aug 10, 2009 6:10 pm; Thanked: 653 times; Followed by:252 members

Re: Can You please explain this

by papgust » Tue Oct 20, 2009 12:49 am

navdeepbajwa wrote:Why the answer is 10% and not 7% I am confused and how question can be rephrased if answer needs to be 7%.What is the difference

Two numbers are less than a third number by 30% and 37 % respectively. How much percent is the second number less than the first?

a) 10 % b) 7 % c) 4 % d) 3 %

Solution: .7 & .63

diff in %= (.7 - .63)/.7 * 100= .07/.7 * 100= 10%

Consider Thrid number as 100 (say).
First number is less than 3rd number by 30% ==> 70
Second number is less than 3rd number by 37% ==> 63

Second number is less than first by what?
Here, take percent change b/w second and first.
i.e. (70-63)/70 ==> 1/10 or 10%

Hope this helps

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navdeepbajwa: Senior | Next Rank: 100 Posts; Posts: 74; Joined: Sun Aug 02, 2009 9:10 pm; Thanked: 1 times; Followed by:1 members

re

by navdeepbajwa » Tue Oct 20, 2009 12:59 am

I can't understand this part

diff in %= (.7 - .63)/.7 * 100

why we have to divide by 0.7 why can't it be difference * 100 = 7%

thanks

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papgust: Community Manager; Posts: 1537; Joined: Mon Aug 10, 2009 6:10 pm; Thanked: 653 times; Followed by:252 members

Re: re

by papgust » Tue Oct 20, 2009 1:09 am

navdeepbajwa wrote:I can't understand this part

diff in %= (.7 - .63)/.7 * 100

why we have to divide by 0.7 why can't it be difference * 100 = 7%

thanks

This is the percentage change formula. Let me give a few examples on this,

For example, in 1990, sales is 10,000 and in 1991, sales increased to 11,000. If you are asked to find the % increase in sales, then

% sales increase = (11,000 - 10,000)/10,000 = 10%

Consider this, in 1990, sales is 10,000 and in 1991, sales increased to 9,000. If you are asked to find the % decrease in sales, then

% sales decrease = (10,000 - 9,000)/9,000 = 11.11%

This formula applies not only to integers (such as 10k, 11k). This applies for percentages as well (as is the case in this prob).

Hope this helps!