Find the third proportional to 4 and 8
32
128
64
16
Let the third proportional be b
Hence we have 4 : 8 :: 8 : b are in proportion
Hence 48=8b
4b = 8×8
b = 8×84
= 16
Hence the third proportion to 4 and 8 is 16
Find the third proportional to 16 and 40