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Two families are traveling by car to a camp 280 kilometers away.
One family leaves 20 minutes ahead of the other family and travels at an average speed of 40 kilometers per hour.
What would the speed of the second family’s car need to be if the family is to reach the camp at the same time
as the first family? (Hint: set up two equations, and solve by substitution)
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I don't like when the instruction dictates me how to solve the problem,
because I know the way in 20 times better than those, who write these stupid instructions.
The first family's travel time was = 7 hours.
HENCE, the travel time of the second family must be 20 minutes less, or 6 hours 40 minutes = 6 = hours.
It means, that the second family's average speed must be = = 14*3 = 42 kilometers per hour. ANSWER
Solved (without using any equations).
It is standard classic 4th grade - 5th grade problem, when the children know NOTHING about equations.
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By the way, if you and your child want to learn on using equations for solving Travel & Distance problems,
I recommend you these introductory lessons
- Travel and Distance problems
- Travel and Distance problems for two bodies moving in opposite directions
- Travel and Distance problems for two bodies moving in the same direction (catching up)
in this site.
They are written specially for you (and your child).
You will find the solutions of many similar problems there.
Read them and learn once and for all from these lessons on how to solve simple Travel and Distance problems.
Become an expert in this area.