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T took 5 h to drive 470km from point x to point y.For part of the trip, he drove at 100 km/h, and for the other part, he drove at 90 km/h. How far did he drive at each speed.

So I know that speed 1 distance + speed 2 distance = 470 km. I don't know the rest, however.

thanks

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Hint: There are two unknowns; $T_1$, the time for which he drove on the first part (at $100$ km/h); $T_2$, the time for which he drove on the second part (at $90$ km/h). What is the sum $T_1+T_2$? What is the sum $100T_1+90T_2$? The answers give you 2 equations for the two unknowns.

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  • $\begingroup$ t1+t2=5h and 100t1+90t2=470. $\endgroup$ – a s Mar 3 '15 at 4:42
  • $\begingroup$ Yes! Now you have it. $\endgroup$ – Mark Viola Mar 3 '15 at 4:43

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