## anonymous 5 years ago A Piper Cub has an average air speed that is 10mph faster than a Cessna 150 airplane. If the combined distance traveled by these two small planes is 690 miles after 3 hr, what is the average speed of each plane?

1. anonymous

let x be speed 1, y be speed 2. 3(x+y) = 690. x = y + 10. So Y=110 X= 120 is this correct?

2. anonymous

v1 = 10 + v2

3. anonymous

so I'm wrong?

4. anonymous

well im doing it differently

5. anonymous

do you agree that v1 = 10 + v2

6. anonymous

v1 is the speed of the piper cub

7. anonymous

yes

8. anonymous

ok the distance we know is d = v* t , where v is the speed or rate, like d = rt

9. anonymous

right

10. anonymous

so the total distance you add the distances of the two planes , so v1*3 + (10+v2) *3 = 690

11. anonymous

so you have a system of equations ,

12. anonymous

since you know that v1 = 10 + v2, you can substitute that into the second equation

13. anonymous

ok

14. anonymous

(10 + v2) *3 + (10+v2)*3 = 690

15. anonymous

maybe someone should check my work

16. anonymous

$\sqrt{105}$

17. anonymous

v =10.25695

18. anonymous

i got v2 = 105

19. anonymous

as did I

20. anonymous

so v1 = 115

21. anonymous

hmm, so The first one I did was wrong

22. anonymous

no no nio

23. anonymous

24. anonymous

we had v1 *3 + v2 *3 = 690

25. anonymous

3 ( v1 +v2 ) = 690

26. anonymous

substitute v1 = 10 + v2

27. anonymous

3 ( 10 + v2 + v2) = 690

28. anonymous

so v2 = 110

29. anonymous

so v1 = 100

30. anonymous

i meant

31. anonymous

oh, I got 120, let me check my math

32. anonymous

v1 = 120

33. anonymous

you did everything right

34. anonymous

AWESOME! thank you sooo much!