About Chanda Walker Expertise I can answer word problems involving mathematics at the high school and college level. I particularly enjoy calculus word problems. Please don't just type the math problem without comments. If you don't tell me what problem your having, I can't help.
Experience Have done word problems as a tutor and as a student of mathematics and physics for years.
Organizations Sigma Xi
Education/Credentials Optical Science PhD
Past/Present Clients I've answered hundreds of questions here at AllExperts.com in algebra, physics and general math sections.
Question Zach arrives from Phoenix to somewhere at 60mph. Zach drives back from
somewhere to Phoenix at 40mph. What is his average speed?
Is this just simply adding 60+40 and dividing by 2 to get 50mph?
Answer No not quite . . .
Let x = the distance traveled between Phoenix and somewhere.
He took x/60 hours to get there. (If the distance were 120miles you can see it would be 2 hours.)
Now, on the way back he took x/40 hours.
Let's sum these and you'll have how long he traveled.
x/60 + x/40 = 100x/2400 = x/24 hours.
So he traveled 2x miles in x/24 hours.
To get miles per hour you divide the number of miles you traveled (2x) and the number of hours it took you to travel them:
2x/(x/24) = 48 mph
A little counter-intuitive huh. He traveled a longer length of time at the slower speed so the average is less than 50mph.
