Question

EASY MATH PROBLEMS! #8 and #10

Answer 1

8. volume of cylinder is pi*r^2*h
So V= pi * (radius)^2 * height =720* pi

we know circumference = 2 * pi * r

if we look at first equation. We can edit it like
pi * r * r * h

now we can say it kind of looks like circumference equation but missing 2 so we multiply both sides by 2
2 * pi * r * r * h = 2 * 720 * pi

We can take out the 2 * pi * r and put in circumference (C)

c * r * h = 1440 * pi

We we know h is 20 so

c * r * 20 = 1440 * pi
c * r = 72 * pi

we have to solve for r first so break circumference back up

2 * pi * r * r = 72 * pi

r * r = 36
r = 6

plug into circum equation
C = 2 * pi * 6
C = 12 * pi


10. I assume the cylinders fill uo the box and if radius is 1.5 then diameter is 3. There are 5 in a row some 3 * 5 = 15 box length.
2 in a column so 2 * 3 = 6 box width
the height is 5

So
l * h * w = V

6 * 5 * 15 =V

V = 450