how many 0.4 inches in 8 inches?
\(\dfrac{8~in}{0.4~in} = 20\)
We can multiply each by 5, like saying how many 0.4*5 = 2 inches in 8*5 = 40 inches?
That's easier to comprehend.
Can you solve now? How many 2 inches are in 40 inches?