# speed

• Sep 9th 2008, 04:49 AM
2hot2domaths
speed
a cyclist covers 7 1/2 km in 1/2an hour what is the average speed. answer in km per hour. metres pre minute and metres per second
• Sep 9th 2008, 04:54 AM
mr fantastic
Quote:

Originally Posted by 2hot2domaths
a cyclist covers 7 1/2 km in 1/2> Mr F says: Without a unit of time for the 1/2 you're not going to get much help.

what is the average speed. answer in km per hour. metres pre minute and metres per second

Use speed = distance/time.
• Sep 9th 2008, 05:09 AM
mr fantastic
Quote:

Originally Posted by 2hot2domaths
a cyclist covers 7 1/2 km in 1/2an hour what is the average speed. answer in km per hour. metres pre minute and metres per second

Note that 7 1/2 = 15/2.

Speed = distance/time $= \frac{15/2}{1/2} = 15$ km/hr.

15 km/hr = 15000 m in 60 minutes = ...... m/min.

15 km/hr = 15000 m in 3600 seconds = ...... m/sec.
• Sep 9th 2008, 05:14 AM
2hot2domaths
thnx but i still dont understand one bit howdu get that
• Sep 9th 2008, 05:17 AM
mr fantastic
Quote:

Originally Posted by 2hot2domaths
thnx but i still dont understand one bit howdu get that

Which part don't you understand?

7 12/ km in 1/2 hour is equivalent to 15 km in 1 hour, that is, 15 km/hr.