How long will it take a car traveling 40 miles per hour to travel 4 miles?

Answer 1

4/40 = 1/10
One tenth of an hour.
Six minutes

Addition:

You can generate you own equation for things like these using the units you know.

Having any speed (miles/hour) and distance (miles), simply use algebra on the units alone.

Incorrectly multiplying speed and distance would give you (miles*miles)/hour, which doesn't make any sense. If you think about it logically, you wouldn't say, "I'm going 40 miles per hour for 4 miles, so I'll multiply them and it will take 160.. hours?"

Once you get the hang of it, you won't need process of elimination like that to get the right equation, you can just think of the units you want. You asked how LONG it would take, you want time, in hours. How do you get something from the bottom of a fraction to the top? Division. Dividing distance by speed: miles / (miles/hour), the "miles" cancel out and hours moves to the top.

Now you have a general expression to answer any question like that, you know distance/speed gives you the time it would take. Then it follows speed * time gives you distance traveled at that speed, and distance over time gives you speed (obviously),