Bob and Sue enter a race. Bob runs an average of 12 kilometers per hour, and Sue runs an average of 8 kilometers per hour. If Bob finishes 2 hours before Sue, how long is the race?

24 km
96 km
48 km
36 km

Question

Bob and Sue enter a race. Bob runs an average of 12 kilometers per hour, and Sue runs an average of 8 kilometers per hour. If Bob finishes 2 hours before Sue, how long is the race?

24 km
96 km
48 km
36 km

tkhunny · Answer

Distance = Rate * Time

Do a separate version for both runners.

Hint: The distance is the same.

anonymous · Answer

24km?

tkhunny · Answer

You know I want to see how you got that, right?

Bob: 12 kph * h hr = Race Length
Sue: 8 kph * (h+2) hr = Race Length

Set those equal.  Solve for h.  Then use h in either equation to calculate the length of the race.

anonymous · Answer

Noooo my bad! It's 48km. 

At 48 km, Bob is done in 4 hours while Sue is done in 6 hours. 6-4=2 hours difference

tkhunny · Answer

Perfect.