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Math Questions I need help on

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Math Questions I need help on [#permalink] New post 28 Feb 2009, 14:01
So the following 5 math questions I am having difficulty figuring out how to get to the answers given...any help would be much appreciated. Thanks!

1) Fox jeans regularly sell for $15 a pari and Pony Jeans regularly sell for $18 a pair. During a sale these regular unit prices are discounted at different rates so that a total of $9 is saved by purchasing 5 pairs of jeans: 3 pairs of Fox Jeans and 2 pairs of Pony Jeans. If the sum of the two discount rates is 22 percent, what is the discount rate on Pony Jeans?

Answer: 10%

2) If [x] is the greatest integer less than or equal to x, what is the value of [-1.6]+[3.4]+[2.7]?

Answer: 3

--> Since this adds to 4.5 and it says the greatest integer less than or equal to x, I would have thought the answer was 4 (this was one of the choices, but not the right answer so not sure what I'm missing here).

3) Two triangles are shown with the same measurements for each angle: if the base of the smaller triangle is denoted s and the base of the larger triangle is denoted S, what is s in terms of S if the larger triangle has an area 2 times that of the smaller triangle?

Answer: S=s*the square root of 2

4) What is the greatest prime factor of 4^17-2^28

Answer: 7

5) square root of ((9+square root of 80)+square root of(9-square root of 8))^2

Answer: 20
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Re: Math Questions I need help on [#permalink] New post 28 Feb 2009, 15:56
1, 45-0.45x -(36-0.36y) = 9 - eq 1
x+y = 0.22 - eq 2

solve x and y u get y

2, -2 + 3 + 2 = 3 since [x] is the greatest integer less than or equal to x [-1.6] = -2 since -2 is less than -1.6 and a integer similarly the other 2

3, two triangles are equilateral. side is given, hence height = ((sqroot of 3)/2) *a. then use 1/2b*h and equate, u will get s2 = S2

4, simplify 2power34-2power28
2pwr28(2power6-1)
2pwr28(64-1) = 2pwr28(63)
63 is written as 7*9, hence the highest prime factor is 7, since the other factors are 2 and 3

5, i tried it, but got something like sqrt of 18 + sqrt of 19, i think i did not get u r expression right.
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Re: Math Questions I need help on [#permalink] New post 01 Mar 2009, 08:03
thanks, sorry but still confused on a couple of the responses:

1) I don't understand how to find the greatest prime factor of 2^34-2^28...not sure where you got 64 from and how that breaks down.

2) Also, could you explain the two triangle area question? The answer ends up being (square root of 2)*s

3) In the first equation 1, 45-0.45x -(36-0.36y) = 9 - eq 1, why do you use -.45x and -.36y?

I'll try to print screen on the last question.

thanks so much. I really appreciate it.
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Re: Math Questions I need help on [#permalink] New post 01 Mar 2009, 13:01
4, take 2power34 = 2pwr28*2pwr6
take 2pwr28 common, u r left with 2pwr6-1
2pwr6 = 2*2*2*2*2*2 = 64
64-1 = 63 (7*9)

3. Sorry for the typo, given the area of S = 2 area of s
so S2 = 2s2, u get S = sqrt of 2*s

1. 45/100 (%) and 34/100 (%)
Re: Math Questions I need help on   [#permalink] 01 Mar 2009, 13:01
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