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March 24th, 2009, 03:10 AM   #1
 
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percentage % of a number

okay i'm currently studying for a ASVAB test for the military. and they have questions like the one below,

" what number is 5% of 2000 "

how would i solve for something like that?

or they have

" 35% of what number is 70 "

" if 45 is 120% of a number, what is 80% of the same number? "

" if 6 is 24% of a number, what is 40% of the same number? "

" 25% of $900= "

questions like those, please help!
lambofgod is offline  
 
March 24th, 2009, 06:15 AM   #2
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The symbol "%" means "hundredths", so 120% means 120/100 or 1.2, and 5% is 5/100 or 1/20 or 0.05. Hence, in particular, "50%" means "half", "100% of" means "all", "200% of" means "twice", etc.

For problems such as "What number is 5% of 2000?" (or "Find 5% of 2000."), just multiply 0.05 by 2000 to get the answer.

The problem "35% of what number is 70?" corresponds to the equation: (35/100) * x = 70, where x is the number to be found. Dividing both sides of this equation by 0.35 gives x = 70/0.35.

Does this help you enough for you to complete these problems and do the remaining problems?
skipjack is offline  
March 25th, 2009, 04:15 PM   #3
 
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Re: percentage % of a number

Write it literally [word for word]. The = sign is the verb in the sentence, and "of" means "times", or "multiply", as in three quarters of 12 is 9 ... 3/4x12 = 9.

" what number is 5% of 2000 "

N = 5/100x2000 = 100


" 35% of what number is 70 "

35/100xN = 70 Solve for N ...You must be able to do some algebra from past experience. If not, start again.


" if 45 is 120% of a number, what is 80% of the same number? "

45 = 120/100xN Solve for N, then find 80% of N.

etc...
Dave is offline  
March 26th, 2009, 02:48 AM   #4
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Quote:
Originally Posted by lambofgod
if 6 is 24% of a number, what is 40% of the same number?
40% is 40/24 of 24%, i.e., 5/3 of 24%, so the answer is 5/3 of 6, i.e., 10.
skipjack is offline  
March 26th, 2009, 04:31 AM   #5
 
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Re:

Quote:
Originally Posted by skipjack
Quote:
Originally Posted by lambofgod
if 6 is 24% of a number, what is 40% of the same number?
40% is 40/24 of 24%, i.e., 5/3 of 24%, so the answer is 5/3 of 6, i.e., 10.
Why not, as I suggested earlier, a literal translation?

6 is 24% of a number

6 = 24/100xN
N = 6x100/24 = 25

what is 40% of the same number?

N1 = 40/100xN = 40/100x25 = 10
Dave is offline  
March 28th, 2009, 03:52 AM   #6
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No reason why not. I was giving a process suited to mental arithmetic (as I understand it, the ASVAB is a multiple choice test).
skipjack is offline  
March 28th, 2009, 04:12 AM   #7
 
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Re:

Quote:
Originally Posted by skipjack
No reason why not. I was giving a process suited to mental arithmetic (as I understand it, the ASVAB is a multiple choice test).
I hadn't realised that. Of course, one's approach is different for such tests, even as in some math competitions. However, I have always had a passionate dislike of multiple choice, based on personal experiences, and consider that is how some people get their driver's license.
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