Ratio

A ratio indicates how many times one number contains another.

For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8∶6)

Ratios may be scaled up by multiplying with a constant value or scaled down by dividing with a constant value.

Thus (8:6) is equivalent to (8 x 2: 6 x 2) = (16: 12)

   Or (8:6) is equivalent to (8/2:6/2) = (4:3)

 Similarly, the ratio of lemons to oranges is 6∶8 (or 3∶4) and the ratio of oranges to the total amount of fruit is 8∶14 (or 4∶7).

 

Example 1

A Recipe for pancakes uses 3 cups of flour and 2 cups of milk. Find the ratio of flour to milk

So the ratio of flour to milk is 3 : 2

Example 2

In a class of 42 pupils, the ratio of girls to boys is 2:1. How many girls are in the class?

Solution

Total ratio = 2 +1 = 3

Number of girls = (2/3) x 42 = 28

 

Example 3

If of Gala’s salary is shs 16,000. What is his salary?

Solution

Let the salary be x

(1/3)X = 16000

X = 16000 x 3 = 48000

For more examples and exercise download PDF below

Ratios- upper primary

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