Question

A tub contains red, yellow and blue counters. There is ten more yellow than red counters, and the ratio of red to blue counters is 3:4.If there are 20 blue counters, what is the probability of picking a yellow counter?

Answer 1

5/12

Explanation:

A ratio of 3:4 means that red counters make up 3/7 of the sum of red and blue counters and blue counters make up 4/7 of the total sum of red and blue counters.

If there is 20 blue counters, then 20 is 4/7 of the sum of the total red and blue counters.

So we need to solve for the total sum.

`(4)/(7) x = 20`

`4x = 140`

`x = 35`

So the total amount of red and blue counters are 35,

So this means the amount of red counters is 15.

The amount of yellow counters is 25.

So the total number of counters are 60.

So P(Yellow counters)= 25/60= 5/12