Area of a triangle is... 1/2 Base x Height The answer is followed by units squared.
3.15 is half of 6.3.
3.15 x 3.4 = 10.71 yds squared
You have to be very careful how you set this up. For every girl (who counts as 1) there are 3 boys (who count as 3). The total number in the proportion is 3 + 1 =4. You are given a total, but that is both boys and girls. That's why you need the 4.
3/4 = x / 236 Cross multiply
4x = 3 * 236
4x = 708 Divide by 4
x = 708/4
x = 177
There are 177 boys at the school and 236 - 177 = 59 girls.