Joseph Said:

Writing Parallel Resistors/ adding and subtracting fractions?

We Answered:

1/R(total) = Sum(1/R(n))
where n = 1 to number of parallel resistor

R(total) = 1/Sum(1/R(n))
where n = 1 to number of parallel resistor

Jane Said:

What are the biggest problem people face when adding and subtracting fractions?

We Answered:

Fractions is really easy... What makes it difficult is the operations... People get all mixed up with subtracting and adding fractions or even dividing or multiplying fractions. The thing you got to know is. When you add or subtract a fraction, find the common denominator. For divding fractions you will want to convert it into a multiplication fraction by the recipricol of the 2nd fraction. When you multiply fractions, you'll want to reduce first. It takes understanding before practice.

Everett Said:

PLease Help on 4 problems with adding/subtracting fractions?

We Answered:

To add (or subtract) fractions involving variables, the idea is exactly the same as adding fractions with just numbers: we need to find a least common denominator [LCD], multiply each fraction by an appropriate version of 1 to make all of the fractions have the same denominator, add the numerators and put them over the common denominator, and then reduce if possible. To determine the least common denominator when dealing with variables, you must simply multiply together the highest power of every term in the denominators, along with the least common multiple of all of the numeric terms.

15) 5/x - 6/y
LCD = xy (x^1 is the highest power of x in the denominators, y%1 is the highest power of y in the denominators)
to turn x (the denominator of the first fraction) into xy, we need to multiply by y. Similarly, we need to multiply the second denominator by x to get xy:

5/x - 6/y = 5/x * y/y - 6/y * x/x = 5y/xy + 6x/xy = (5y + 6x)/xy

16) Same idea here: LCD = st
n/s - m/t = n/s * t/t - m/t * s/s = nt/st - ms/st = (nt - ms)/st

17) This one's a bit trickier: the denominators are y and y^2. y^2 is the highest power of y, so y^2 is the LCD.

3/y^2 - 2/y = 3/y^2 - 2y/y^2 = (3 - 2y) / y^2

18) Here they're really testing you. The denominators are 5x^2, 10xy, and x^2 * y^2. The highest power of x is 2, for y it's 2, but then you have the 5 and 10 thrown into the mix. The least common multiple of 5 and 10 is 10, so we need
10x^2 * y^2

1/5x^2 + 3/10xy - 4/x^2 y^2 =
[1/5x^2 * 2y^2/2y^2] + [3/10xy * xy/xy] - [4/x^2 y^2 * 10/10] =
2y^2/10x^2 y^2 + 3xy / 10x^2 y^2 - 40 / 10x^2 y^2 =
[2y^2 + 3xy - 40] / 10x^2 y^2

Natalie Said:

Can someone go over the rules of adding/ subtracting fractions?

We Answered:

make sure the denominators of the fractions you are adding or subtracting are the same
example 3/4 +6/8
a common factor for 4 and 8 is 8, so to turn the 4 into an 8 you must multiply 4*2, therefore you also multiply 3*2. because 8*1=8 you can keep the 6 a 6
3/4 +6/8
6/8+6/8 = 12/8
simplified, 12/8 = 3/4

Kay Said:

I am a old fart with problems in solving fractions. Especially when it come to adding and subtracting fraction?

We Answered:

Find the LCD, which is like acid. Yummy!

Mitchell Said:

Most important thing u can say about adding/subtracting fractions to someone who didnt learn about fractions?

We Answered:

Making the denominators the same.