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| Math Central | Quandaries & Queries |
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Question from MJ, a student: If a truck increases its average speed by 10 km/h it can cover 60 km at the original speed in the same time that it can cover 80 km at the faster speed. What is the original speed? |
H MJ,
The key here is that "distance equals time times rate." For the slower trip let the time be $t$ hours and the rate be $r$ km/hr. You know the distance is 60 km so write the expression for "distance equals time times rate."
For the faster trip what is the rate, distance and time? Write the expression for "distance equals time times rate."
Solve each of the expressions for $t,$ set them equal and solve for $r.$
Penny
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