Question

At a school fair, 70% of the people are under 16 years old. One-third of the people remaining are teachers. If there are 21 teachers at the fair, how many people are there at the fair total? A. 63, B. 126, C. 189, D. 210. Please I need help.

Answer 1

So, "one third of remaing" is 21, this means that the "remaining" was three times as much: 21*3=63

This 63 is the 30 % of all the people, since they are the remaining of 100-70%.

so: 63=30/100x

we now multiply both sides by 100:

6300=30x

and divide by 30:
210

so all the people at the fair numbered 210!