Answers

2016-02-25T20:11:32+08:00
1. For example, you need to find the value of a missing number:
3 : 6 = x : 72
The product of the means, must be equal to the product of the extremes. 
6x = 72(3)
6x = 216
 \frac{6x}{6}= \frac{216}{6}
x = 36
          3 : 6 = 36 : 72


2. For example, there were two values missing. (Same question I've encountered here at brainly)
x : 8 = y : 56
Make sure that when you gave a value for the missing number in the first ratio (which is x is to 8 in my example), the ratio must be not reduce in lower term. So, we'll have x = 7. Now, we just need to find the value of y.
8y = 56(7)
 \frac{8y}{8} = \frac{392}{8}
y = 49 
             7 : 8 = 49 : 56

3. Partitive proportion. The sum of the numbers were given. For example, you have this question: The sum of three numbers having a ratio of 2 : 3 : 4 is 45. What's their value?
2x + 3x + 4x = 45
 \frac{9x}{9} = \frac{45}{9}
x = 5
2(5) = 10
3(5) = 15
4(5) = 20
            2 : 3 : 4 = 10 : 15 : 20

4. Same. For example, you have this question: The product of two numbers having a ratio of 2 : 5 is 90. What are the two numbers?
(2x)(5x) = 90
10x² = 90
 \frac{10x^2}{10} = \frac{90}{10}
 \sqrt{x^2} = \sqrt{9}
x = 3
2(3) = 6
5(3) = 15
                       2 : 5 = 6 : 15

Those are just some examples. I hope that my answer'll help. ^-^
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