# A radio station's signal has a radius of 100 miles. If you drive at a constant speed of 40 miles an hour, non stop, directly across the diameter of the signal; how long can you listen to the station before the signal fades?

2 and half

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It's quite easy to work out how long you can listen to a radio station before the signal fades if you're travelling at 40 miles an hour across the diameter of the 100-mile radius signal. The best thing to do is break it down!

Firstly, let's be clear on what radius and diameter mean.

• Radius - the distance of a circle from the middle to the outside.

• Diameter - the distance across the whole of the circle. It is double the radius.

1. The radius of the signal is 100 miles, and since the diameter is double the radius, you'll be driving 200 miles.
2. You're travelling at 40 miles an hour, so to work this out you can do a simple division sum: 200/40=5. Alternatively, you could count how many 40's go into 200... The answer is 5!
3. So there you have it. You can drive for 5 hours at 40 miles an hour listening to the radio before the signal fades. Hope this helps!

It looks like someone has already asked this question. Take a look at this version to find out some different ways of working the problem out: http://entertainment.blurtit.com/3105468/a-radio-stations-signal-has-a-radius-of-100-miles-if-you-drive-at-a-constant-speed-of-40

This video is kinda cool, you can learn about the maths behind circles through music! Take a look below:

thanked the writer.