How many children does Brenda's family actually have? (I)Algebra Level 2
When Mrs Tan was pregnant with Billy, the average age of her children was 20.
When Billy was born, their average age became 16.
How many children does Mrs Tan have with the new addition?
Many of you might consider the possibility of birthdays occurring during the pregnancy period but even then there is only ONE possible answer to this question. Can you work out what it is?