# I have a question about Calculating Avreage Speed

1. Sep 9, 2009

### _wantana

The question states that Running a marathon backwards the record is 3 h 53 min 17 s and the race is 42.2 km's and im supposed to calculate avreage speed of the race in meters per second and kilometres per hour I found a way to convert the record into just hours and I divided by 42.2 and the answer was completely wrong because according to the book its 10.9km/h and 3.01m/s does anyone have any idea how to acheive this answer?

2. Sep 9, 2009

### Jebus_Chris

$$s=\frac{d}{t}$$
Speed is km/h, not h/km.

3. Sep 9, 2009

### rl.bhat

Show your conversion of time to hour.

4. Sep 9, 2009

### _wantana

3 h 53min 17 s >3.29805556 hours

5. Sep 9, 2009

Now v = d/t.