X = D/(1 - h)
1 - h = D/x
h = 1 - D/x
D = 400, X = 4000
h = 1 - 400/4000
h = 1 - 0.1 = 0.9
Answer
A. 129.3
B. The students ages can be any number within the ranges, so having the middle number wont represent the other possible heights.
Step by step
'h' is the number between the surrounding number, the first would be 122.
You need to multiply the hight by frequency of each one,
122x7 =854
126x8=1008
130x13=1690
134x9=1206
138x3=414
Add them up = 5172
5172/40 =129.3
