avearge speed over a set distance

[W Sussex Sue]

If you wanted to travel a set distance at an average speed of 60 mph, would you do it by (a) travelling for half the time at 50 mph and half at 70 mph or,

(b) travelling half the distance at 50 mph and the other half at 70 mph ?

[Buenchico]

Answered here:
http://www.theanswerbank.co.uk/Motoring/Questi on544457.html

Chris

[sddsddean]

Lets assume your set distance is 60 miles, so that at 60mph it takes 60 minutes. Remember distance = velocity x time. So in your scenario a) 30 mins at 50 mph, you travel 25 miles; 30 mins at 70 mph, you travel 35 miles. 25 + 35 = 60, so this works. In b), at 50 mph it takes 36 mins to cover 30 miles; at 70 mph it takes 25.71 mins to cover 30 miles. 36 +25.71 = 51.71 mins (not 60), so this doesn't work. So answer to your question is a).

[W Sussex Sue]

Thanks to both buenchico and sddsddean for your quick help and very understandable explanations.
WSS