1. ## Distance problem

Carmen drove from Blairtown to Ore City, a distance of 80 miles. From Ore City she drove to Janesville, and the drove back to Blairtown. The ratio of Carmen's driving times on the first, second, and third segments of the trip, respectively, was 5:2:4, and she drove at the same average speed on each segment. What was Carmen's total driving distance, in miles, for the 3 segments of the trip?

I know it is 176, but how do I show it algebraically?

2. ## Re: Distance problem

Hint: Since the average speed is the same, the ratio of distances is the same as the ratio of times. Indeed, let's say it took $t_1$ hours to drive from Blairtown to Ore City and $t_2$ hours to drive from Ore City to Janesville, and let the average speed be $v$. Then the distance between Blairtown and Ore City is $vt_1$ and the distance between Ore City and Janesville is $vt_2$. The ratio of these distances is $\frac{vt_1}{vt_2}=\frac{t_1}{t_2}=\frac{5}{2}$ is the same as the ratio of times.

3. ## Re: Distance problem

Right, but how do i show it with 3 ratios?

4. ## Re: Distance problem

$\frac{5}{80} = \frac{2}{x}$, x = 32 is the distance from Ore city to janesville.

$\frac{5}{80} = \frac{4}{x}$, x = 64 is the distance from janesville to blairtown.

so 64+32+80 = 176 is total driving distance

5. ## Re: Distance problem

Originally Posted by jakncoke
$\frac{5}{80} = \frac{x}{2}$, x = 32 is the distance from Ore city to janesville.
Hmm, there is something wrong about this proportion. I would say, 80 : x = 5 : 2 where x is the distance from Ore City and Janesville.

6. ## Re: Distance problem

Originally Posted by emakarov
Hmm, there is something wrong about this proportion. I would say, 80 : x = 5 : 2 where x is the distance from Ore City and Janesville.
yes, i miswrote, i corrected it.