# Homework Help: Physics convert units

1. Jan 19, 2012

### samona

1. The problem statement, all variables and given/known data

A large school district has 300 school buses. If each school bus is used 3 hours each day, the average speed of the school buses is 15 mi/h, and the fuel economy of the buses is 10 mi/gal. How much does it cost to run these buses in 22 school days if gasoline costs $1.20 a gallon? 2. The attempt at a solution I've been trying to figure out this problem for hours now. This is what I've done, but the book says I'm incorrect. My attempt: Find out what it costs to run one bus a day. 3 hrs/day x 15 mi/hr x 1gal/10mi x$1.20/gal = $5.40 per day for 1 bus. There are 300 buses, so$5.40 x 300 = $1620 for 300 buses. The problem asks the cost for running the buses for 22 school days,$1620 * 22 = $35,640. My final answer is that it would cost$35,640 to run 300 buses for 22 days. Please help me figure out where I am going wrong.

2. Jan 19, 2012

### phyzguy

Your analysis looks good to me. What does the book say is the right answer?

3. Jan 19, 2012

Thanks for the quick response. The answer seems to be $216. 4. Jan 19, 2012 ### phyzguy I think that$216 can't possibly be the right answer to the problem you posed. Are you sure you copied it correctly?

5. Jan 19, 2012

### samona

I'll double check when I get home tonight. I appreciate your help!

6. Jan 19, 2012