## kaiteDID 3 years ago At 10:00 a.m. two planes leave an airport. If the northbound plane flies at 280 mph and the southbound at 320 mph, at what time will they be 1,000 miles apart? { a.m.}

1. CliffSedge

Distance = speed × time.

2. CliffSedge

There are two distances and two speeds, but the two distances add up to 1000mi. and the time for both is the same.

3. kaiteDID

how does 320+280=1000

4. CliffSedge

320×time + 280×time = 1000.

5. CliffSedge

You have to find the time.

6. CliffSedge

"320+280=1000" would be 'speed + speed = distance' which doesn't make sense.

7. kaiteDID

so speed + speed = distance means that it equals 600?

8. CliffSedge

Speed + speed = distance is nonsensical and cannot be used. There are two distances that add up to 1000, so you need distance1 + distance2 = total distance. distance1=speed1×time, distance2=speed2×time. The only unknown here is the amount of time.

9. kaiteDID

so confusing

10. CliffSedge

It does reduce to an equation that looks like a single speed of 600mph, and a single time of ? for a single total distance of 1000mi.

11. CliffSedge

|dw:1349967841261:dw|

12. kaiteDID

okay

13. CliffSedge

Go back through everything I wrote a little at a time and think about it. I'm sure you'll figure it out.

14. kaiteDID

is the time 4:00 a.m.?