Question

13 There are some people in a cinema.
3
of the people in the cinema are children.
5
For the children in the cinema,
number of girls : number of boys = 2:7
There are 170 girls in the cinema.
Work out the number of adults in the cinema.​

Answer 1

Answer:

We can begin by working out the total number of children in the cinema. We know that for every 2 girls, there are 7 boys, which is the same as saying for every 1 girl, there are 3.5 boys. Three and a half boys sounds a bit silly, but stick with me! :)So, as there are 170 girls, there are 170 x 3.5 = 595 boys.Adding the girls and the boys together, we get 170+595=765 children in total.

Now, we know already that these children make up 3/5 of the total number of people, which means adults must make up 2/5 of the total.If 765 children is equal to 3/5, then we work out 1/5 by dividing this by 3, and we get 765/3=255.But the adults make up 2/5, so we have to multiply this number by two! Therefore there are 2 x 255 = 510 adults.