Ali walked 1km in 12 minuets. He stopped for 10 minuets and then walked a further 3km in 38 minuets. Calculate his average speed in km/h. I understand that average speed = total distance dive total time , so should I add the time ali stopped as well? Can anyone help please? Thanks.

Yes, you would add the time he stopped too. What counts, is the time he departed and the time he arrived.

Can you give what you get? :)

So he walked 4km in 60mins so it is... 4 divide 60? Which is 0.06?

Hm... not quite.

What you got is the speed in km/min

Convert into hours as you were asked now.

In 1 minute, he covers 0.06666 km
In 60 minutes, he covers 0.06666 x 60 = 4 km/hr

3.9996? I am confused :S

Right, but you didn't take all the numbers.

The actual distance he covers in 1 minute is \frac{4}{60}

Multiply that by 60, to get:

\frac{4}{60} \times 60 = 4

So is it 4km/h?

Yes it is :)

Thank you , and possibly 1 last question? I have posted it on average speed 3 , and have used what you taught me , darren ran a 200m race in 24 seconds what was his average speed for the race in m/s? Is it 8.3m/s and his av sp in km/h 20.88 km/h

a. Darren ran a 200m race in 24 seconds. What was his average speed for the race in m/s. Is it 8.3? And also I have to find his average speed in km/h. can anyone help with both questions please?

i have posted it on average speed 3 , and have used what you taught me , darren ran a 200m race in 24 seconds what was his average speed for the race in m/s? Is it 8.3m/s and his av sp in km/h 20.88 km/h

1. Right
2. Not quite...

200 m = 0.2 km
24 s = \frac{24}{60}\ min = \frac{24}{3600}\ hours

So, speed = 0.2 \div \frac{24}{3600} = 0.2 \times \frac{3600}{24} = 30\ km/h

Or from you initial speed:

8.33\ m/s = 8\frac13\ m/s = 8\frac13\ m/s\ \times\ \frac{3600s}{1000m}\ =\ 30\ km/h