Question 21

Thursday, November 5, 2009
21. Andrew drove his car 234 km from Dawson to Mayo in Yukon Territory in 3h. Brian drove his truck along the same route at an average speed of 5km/h greater than Andrew's average speed. How much less time did Brian take, to the nearest minute?

First you need to find out Andrew's average speed to find out Brian's average speed.

Andrew took 3 hours to drive 234 km. This would look like 234 km/3h. The average speed is always per hour, right? So you'd need to divide 234 km by 3.

So Andrew's average speed is 78 km/h. Brian is driving 5 km/h greater than Andrew. So 78 plus 5 would be 83. Therefore, Brian is driving at 83 km/h.

We need to find out how much less time Brian took, right? To do that we actually need to know how much time Brian took to get to Mayo.

So Brian's driving 83 km/h and the distance from Dawson to Mayo is 234 km so we need to divide 234 km by 83.

It took him 2.819277108 hours. Of course that's kind of ridiculous so we need to find out how much time that would be in simpler terms.

There are 60 minutes in an hour, right? I think it might be easier to find out the answer if you convert it into minutes. So he takes 2.819277108 hours to get there. 2.819277108 multiplied by 60 is...

It's 169.1566265. Just round that off to 169 minutes. So now we know Brian takes 169 minutes to get from Dawson to Mayo.

To make things easier, I'll just tell you that Andrew took 180 minutes to get from Dawson to Mayo. (3 multiplied by 60)

Now all you need to do is find the difference in their times.

So this means that Brian took 11 minutes less time to go to Mayo from Dawson than Andrew.


shaneille 9-05 said...

Great Job Aleiah! I like how you put pictures and lots of colour, i also liked how you changed the formula. I mean instead of finding how fast his friend goes, you found how fast he went and added five. Did that make sense? Anyways Great job again!

linda 9-05 said...

Hey Aleiah, awesome post here! I was seriously confused about this question, and you really helped me out! Your explanations are excellent!

Zerlina905 said...

Nice post Aleiah! Thanks for explaining the post. This was one of the ones that gave me a hard time. I missed just a few steps. Now it totally makes sense now! Great explinations and pictures. Great job!

Lissa 9-05 said...

Good job Aleiah! Great explanations! Your explanations are very easy to understand. Keep up the great work!

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