How do you do Poportions in math?

Answer 1

Assuming you mean proportions, or fractions equalling each other, there are two ways to do this:

First, take the following problem;

5/7 = x/63

Take the highest number denominator and divided it by the lowest denominator. In this case, divide 63 by 7:

63/7 = ?

Take your answer and multiply by the given numerator, which in our example is 5:

63/7 = 9

9 x 5 = 45

Therefore: 5/7 = 45/63

The second way to do this is to cross-multiply and then divide:

5/7 = x/63

7x = 5 x 63

7x = 135

7x/7 = 135/7

x = 45

The method is slightly different if the variable is a denominator:

2/x = 18/72

One method is similar to the method given above, but with one slight change. Divide the larger of the two numerators by the smallest, then divide the given denominator by that solution:

2/x = 18/72

18/2 = 9

72/9 = 8

x = 8

2/8 = 18/72

The second method prescribed above will work for the denominator:

2/x = 18/72

18x = 2 x 72

18x = 144

x = 144/18

x = 8

2/8 = 18/72

Answer 2

a/b = c/d implies bc = cd. This is called cross multiplying.
For example does 5/8 = 25/40?
Cross multiply getting 8*25 = 5*40 or 200 = 200 so it does

In the proportion a/b= c/d, a and d are called the extremaes and b and c are called the means. The product of the means = the product of the extremes.

So if ab=cd, either pair can be made the extremes and the other made the extremes. This m eans that
a/b = c/d is the same as b/d= c/a because cross multiplying gives the same result in both cases.

So if x/5 = 2/3
then 3x=10 and x= 10/3 = 3 1/3

If 2/x= 5/6, then 5x = 12 and x= 12/5 = 2 2/5

Answer 3

Hi,

To do proportions,set 2 fractions equal to each other. then cross-multiply and set the 2 expressions equal to each other. Solve the resulting equation.

For the proportion:

7........x
----.=.---
12 60

cross-multiply to get:

7(60) = 12x

Now simplify the expression and solve for x.
420 = 12x
35 = x <== answer


For the proportion:
5.........x + 3
----.=.--------
15........18

cross multiply to get the equation:

5(18) = 15(x + 3)
Now simplify the expression and solve for x.

90 = 15x + 45
45 = 15x
3 = x


For the proportion:

..2.........x-3
------.=.------
x+2........7

cross multiply to get the equation:

2(7) = (x+2)(x - 3)
Now simplify the expression and solve for x.

14 = x² - x - 6
0 = x² - x - 20

This factors into:

0 = (x - 5)(x + 4)

This solves to give 2 answers:

x - 5 = 0
x = 5 <== 1st answer
x + 4 = 0
x = -4 <== 2nd answer

I hope those give you examples to understand proportions!!
:-)