1)The average height of 4 boys is 1.65m. One boy is 1.68m tall. Find the average height of the other 3 boys. 2) Ian, John and Juan shared a sum of money in the ratio 4:7:9. What percentage of the sum of money did John receive?
3) The usual price of a refrigerator is $800. It is sold at a discount of 15%.find the selling price.

1)
If the average height of the 4 boys is 1.65m that means the total of their heights is 6.6m

To get the average height of the other 3 boys you have to take away the one boys height from the total and divide that number by 3

6.6-1.68 = 4.92
4.92/3 = 1.64

Therefore the average height of the other three boys is 1.64m

2)
To do this you first find the total of the parts of the ratio so
4+7+9 = 20

Next you find what percentage each part is worth so
100/20 = 5
This means that each part of the ratio is worth 5% of the total sum

Because John received the 7 in the 4:7:9 ratio you times 7 by 5
7x5 = 35

Therefore John got 35% of the total sum of the money

3)
The formula for finding the discounted price using the percentage discount is
Discounted Sale price = (100% - %Discount) x Regular Sale Price

Using this formula to find the discounted sale price you do

(100% - 15%) x 800
= 85% x 800
= 680
Therefore the selling price of the refrigerator is $680