Question

At a school fair 70% of the people are under 16 years old. One-third of the people remaning are teachers. If there are 21 teachers at the fair, how many people are there at the fair total

Answer 1

30% remains
a third of 30% is 10%
so 10% are teachers
21 (amount of teachers) × 10 = 210
answer = 210

Answer 2

Let's write out what we do know...

70% of the people are under 16 years old

From this information, we can infer that 30% of the people are 16 or older.

100%-70%=30%

1/3 of the people 16 or older are teachers. There are 21 teachers.

1/3 of 30% is 10%

1/3*.30=.10 or 10%

So 21 is 10% the total number of people at the fair.

$\frac{10}{100}= \frac{21}{x} 2100=10x 210=x$

(I cross multiplied and then divided both sides by 10 to get x=210)

There are 210 people at the fair.