math
posted by Kim on .
Please help
A school had 900 students at the start of a school year. If there is an enrollment increase of 7% by the beginning of the year, what is the new enrollment?
A virus scanning program is checking every file for viruses. It has completed checking 40% of the files in 300 seconds. How long should it like to check all the files?
Gasoline accounts for 85% of the motor fuel consumed in the United States every day. If 8,882 thousand barrels (bbl)of mototr fuel is consumed each day, how much gasoline is consumed each day in the United States? Round to the nearest barrel.

for the first evaluate 900 + .07*900 or just do
1.07*900
for the second let the total time taken be x minutes, then solve
.4x = 300
Do the third the same way. 
You need to find 7% of 900. Turn you percent into a decimal (.07) and multiply by 900. Add this answer to your original number (900) and you will have the answer.
The easiest way I can think of to do this one is to set it up like a proportion. 40% takes 300 sec. so 100% will take ?
40/300 = 100/x Multiply top to bottom and divide by the other number 300 x 100 then divide by 40.
You are looking for 85% of 8,882 so just turn the percent to a decimal and multiply. Make sure your answers make sense! 
7550 bbl a day