Question

In a bag, Bag C, the ratio of red counters to yellow counters is 3 : 4.

If 3 of the red counters are removed from Bag C, the ratio of red counters
to yellow counters is 3 : 5.

How many yellow counters are in Bag C?

Answer 1

20

Explanation:

The ratio of red : yellow is 3 : 4 = 3x : 4x ( x is a multiplier )

If 3 red counters are removed then

red : yellow = 3x - 3 : 4x = 3 : 5

Expressing in fractional form

`(3x-3)/(4x)` =
`(3)/(5)` ( cross- multiply )

5(3x - 3) = 12x

15x - 15 = 12x ( subtract 12x from both sides )

3x - 15 = 0 ( add 15 to both sides )

3x = 15 ( divide both sides by 3 )

x = 5

Then

number of yellow counters = 4x = 4 × 5 = 20