A bag contains 4 red counters and some blue counters in the ratio 1:4 respectively. How many counters are there in the bag altogether?

Calculate how many blue counters there are first. 4 divided by 1 = 4.4 multiplied by 4 = 16.16 blue counters in the bag.4 red counters and 16 blue counters makes 20 counters in the bag.