First you need the formula for SA of a cylinder: SA = 2(πr^2) + 2πr*h
(area of the top and bottom circles plus the side)
Then plug your values into the equation and rearrange to make h the subject:
1470.3 = 2π13^2 + 2π*13*h
26πh = 1470.3 - 338π
h = (1470.3 - 338π)/26π
=5.00042...
so h is approximately 5 units :)
Julie would reach her goal first. Julie would reach her goal in approximately 316 days while it would take Mary approximately 333 days to reach it.
I know this because the steps to solve the problem are:
1.) 1,000/12 = 83.333 (to find how many days it would take her everyday)
2.) 83.333x4 = 333 (multiplying the answer by four makes it every four days)
3.) determine that it takes Mary 333 days
4.) 1,000/19 = 52.631 (just like step 1 but with different numbers)
5.) 52.631x6 = 316 (just like in step 2 but different numbers)
6.) determine it takes Julie 316 days
7.) 316 < 333 (takes Julie less time)
Multiply 2/3 by the reciprocal, 3/2, on both sides.
