Since it as at the same time and place.
Let x be the length of the shadow of the 40-ft pole.
The ratio from 30 and 8 would have to be the same as 40 and x.
30:8 = 40:x
30/8 = 40/x Cross multiply
30x = 40*8
x = 40*8 / 30 = 32/3 = 10.67
Length of shadow for 40ft is 10.67 ft.