Work out the area of this semi circle

39.27

Step-by-step explanation:

The area of a semi-circle is pi times the radius squared divided by 2. So basically standard area of a circle formula (pi times the radius squared) but then you add in the extra step of dividing it by 2.

The formula looks like this:

π × r² ÷ 2

The radius is half the diameter of the circle. So basically think of it as a line to the middle of the circle. Our diameter is 10, (the diameter is the entire length of the circle. It gives us this already. If you need diameter and only have the radius add the radius together twice or multiply it by 2 to get the diameter. Fun fact..?)

and it tells us to substitute pi for 3.142.

So, plugging our numbers in we get:

3.142 x 5^2 ÷ 2 = 39.275.

Cut out the 3rd decimal place (5) as it tells us to only include the first 2 decimal places, and we finally end up with 39.27.

Hope this helps and have a nice day!

36 girls

step-by-step explanation:

the 48 boys is 4 parts of the ratio

divide 48 by 4 to obtain one part of the ratio

= 12 ← 1 part of the ratio

3 parts = 3 × 12 = 36 ← number of girls