Suppose that 9% of births are twins. If we assume no other multiple births (triplets, etc.), what percentage of the population are twins?

Question

Hint 1:The answer is not 9% or 18%. Hint 2: Do not confuse the given percentage of births with
the percentage of the population. Hint 3: Use 100 births to calculate the answer.

Answer 1

We are given that 9% of every 100 births results in twins.

 

Thus, 91% of every 100 births result in a single child.

 

So. 9% of every 100 births will produce 18 children

And, 91% of every 100 births will produce 91 children.

 

So, our total population will be 109 children.

 

18/109 = 16.5%, and 91/109 = 83.5%