Ratio counters in a bag

Question

There are some red counters and some yellow counters in a bag.

There are 30 yellow counters in the bag.

The ratio of the number of red counters to the number of yellow counters is 1:6

Work out the number of red counters in the bag.

 

Answer 1

red : yellow :: 1 : 6    proportion

red : 30 :: 1 : 6          substitution

30 = 6 red                 product means/extremes

5 = red                     divide both sides by 6