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Y+2/5

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Y+2/5

by [email protected] » Mon Nov 01, 2010 12:10 pm
Hey guys, sorry but I have a small stupid question.

How do you write Y+2/5 as a fraction. the answer is 5Y+2/2...but how do you get that

could you also plz explain me the following questions, the answer is written behind it, but I need to know how to get it:

1/a+2/b.1/2 answer: b+a/ab

4/7-(x+8/7x) answer:3x-8/7x

1/3 - (5/3)a + (5/6)a + 3/8 answer: (-5/6)a + 17/24

2/5(p-4) + 3((1/3)p-1/9) answer: (7/5)p-29/15

((5/12)y+2/3)(12/5-3q) answer: y-5/4yq+8/5-2q

can you smart people plz tell me how they get the answer.
your help is very much appreciated.

regards.
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by Dani@MasterGMAT » Tue Nov 02, 2010 7:16 am
Use the bowtie method for adding and subtracting fractions. Draw three arrows (see diagram). Multiply across each arrow, and place the quantity at the arrow tip. Then add or subtract (depending on what you need) across the top of the new fraction.
For example, 1/6 + 1/8 will work out as:


Image

If you're subtracting fractions (i.e. 1/6-1/8), then subtract across the top of the bowtie as well.

Try this on your calculations. Whenever you're adding an integer and a fraction (for example, y+2/5), place the integer over the 1 and continue with the bowtie.
In other words:
y+2/5 becomes y/1 + 2/5 which after the bowtie becomes = y*5 + 2*1 / 5*1 = (5y+2)/5

Hope this helps.
Dr. Dani Noy
Senior Instructor
Master GMAT
1-888-780-GMAT
https://www.mastergmat.com
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by [email protected] » Tue Nov 02, 2010 10:53 am
Dear sir,
once again thank you for your help.

but could you also plz explain me the following:

y=56x^2

if x = 6

then it would be 56.6^2

then which actions do I need to take first?
6^2 and then multiply by 56?
or 56^2.6^2?

reagards
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by Dani@MasterGMAT » Tue Nov 02, 2010 11:58 pm
[email protected] wrote:Dear sir,
once again thank you for your help.

but could you also plz explain me the following:

y=56x^2

if x = 6

then it would be 56.6^2

then which actions do I need to take first?
6^2 and then multiply by 56?
or 56^2.6^2?

reagards
Remember order of operations: PEMDAS
Parentheses
Exponents
Multiplication
Division
Addition
Subtraction.

Since Exponents come before Multiplication, you first raise 6 to the power of 2 =36, then multiply times 56. 56x^2 becomes 56*6^2.
In order to raise the 56 as well, you would need to place a parentheses around the original, so that everything in the parentheses is raised to the 2nd power: not 56x^2, but (56x)^2, which would then expand into 56^2*x^2.
Dr. Dani Noy
Senior Instructor
Master GMAT
1-888-780-GMAT
https://www.mastergmat.com
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