We know that
the area A of the circular cross section of the pipe is
A=pi*r²
D=20 cm------------- > r=D/2=20/2=10 cm
then
A=pi*10²=100*pi cm²
the answer is A=100*pi cm²
Set up a proportion.
10/5=x/7
5x = 70
x = 14
Find the difference between the 2 numbers which will give you the increase from the lower value to the higher. Divide this increase by the original (lower) number and multiply the result by 100 to get the percentage. For us that looks like this:

. Simplifying a bit we have

or 49%, rounded.
Answer:
I need help too...............
The way i did that in middle school was plot the points then find the slpoe and work it out from there