## gianarpt 2 years ago Im so freaking confused and stupid help me

1. gianarpt

All of the questions are based off of this word problem: efren leaves home at 9am and walks 4 mph. his bro greg leaves 1/2 hr later and runs 8.5 mph in the same direction as efren. predict the time at which gred will catch up to efren

2. gianarpt

write an expression for the distance of greg's travels per hour let h stand for time in hours!

3. gianarpt

write an expression for the distance efren travels per hour plus the distance he will have traveled when greg leaves the house

4. jim_thompson5910

if greg runs at a speed of 8.5 mph and he runs for h hours, how far will he run?

5. gianarpt

i dont know

6. gianarpt

im really stupid no joke when it comes to math

7. jim_thompson5910

you're not stupid, you just need more practice

8. jim_thompson5910

say he ran for 1 hour how far would he get?

9. gianarpt

8.5 miles?

10. jim_thompson5910

good, in 2 hours he will go ____ miles

11. gianarpt

17

12. jim_thompson5910

how did you get that

13. gianarpt

8.5 x 2

14. jim_thompson5910

so in 3 hours, he will run 8.5 x 3 = 25.5 miles so in 4 hours, he will run 8.5 x 4 = 34 miles .... in general... if he runs h hours (some unknown amount of hours), then he will run 8.5 x h or just 8.5h miles

15. jim_thompson5910

so if d = distance traveled, then d = 8.5h

16. gianarpt

oh okay so it says write an expression but im confused on how to write one

17. jim_thompson5910

ok so you'll just write 8.5h

18. jim_thompson5910

8.5h is the expression d = 8.5h is the equation

19. gianarpt

what about the other expression i have to write for efren

20. jim_thompson5910

keep in mind that greg started 1/2 hour later than efren

21. jim_thompson5910

so you have to account for that

22. gianarpt

oh & it says plus the distance he wil he will have traveled when greg leaves

23. jim_thompson5910

let's assume they both start at the same time (9:30 am) if efren walks at 4 mph and he does this for h hours, then he will walk a total of 4h miles

24. gianarpt

so would it be greg leaving at 9:30??

25. jim_thompson5910

but this isn't the whole story because efren leaves at 9:00 am instead of 9:30 am so he's got a 1/2 hr head start

26. gianarpt

okay

27. gianarpt

but i dont know what the distance formula is either thats one of the questions

28. jim_thompson5910

so you have to add in the fact that he walked some additional distance in that half hour where he got the head start if he walked 0.5 hours (1/2 hr) at a speed of 4 mph, then he would have walked 4*0.5 = 2 miles

29. jim_thompson5910

distance formula: distance = rate x time d = r x t d = rt

30. jim_thompson5910

rate is known as speed

31. gianarpt

oh yeah i remember that lol

32. gianarpt

so he walked 2 miles??

33. jim_thompson5910

yes in that half hour where he got the head start

34. jim_thompson5910

so he walked 2 miles in the first half hour then he walked an additional 4h miles after 9:30 am

35. jim_thompson5910

in total, efren walked 2+4h or 4h + 2 miles

36. gianarpt

so what expression would be for efren plus the distance he would of traveled when greg left

37. jim_thompson5910

4h + 2

38. jim_thompson5910

4h is the amount he traveled when greg left 2 is the amount he traveled when greg was still at home

39. gianarpt

oh i see, sorry ive been up all night doing this and im annoyed and fed up :(

40. jim_thompson5910

thats ok

41. jim_thompson5910

to find out when the two will meet, you just set the two expressions equal to one another

42. jim_thompson5910

8.5h = 4h + 2 and solve for h

43. gianarpt

so the next question is weird it says write an equation setting the distance expressions in steps 3 and 4 equal

44. jim_thompson5910

yep you want to find out when the two will walk the same distance (ie find out when/where the two will meet)

45. gianarpt

could you help me figure that out ill try to do most my self

46. jim_thompson5910

well you see how i got 8.5h = 4h + 2 right?

47. gianarpt

yup!

48. gianarpt

you added the time he waited to the expression

49. jim_thompson5910

ok great, subtract 4h from both sides 8.5h = 4h + 2 8.5h - 4h = 2 4.5h = 2 what's next?

50. gianarpt

4.5 = 2 - 2 ?

51. jim_thompson5910

4.5h is the same as 4.5 x h

52. jim_thompson5910

how do you undo multiplication

53. gianarpt

OH! :) I know!! 4.5h/4.5 2/4.5

54. gianarpt

you divide 2 by 4.5

55. gianarpt

am i right?

56. jim_thompson5910

you are correct

57. jim_thompson5910

so h = ??

58. jim_thompson5910

2/4.5 = ?

59. gianarpt

h = 0.4 repeating (so line over the 4)

60. jim_thompson5910

so that's the rough approximation of how many hours it will take (after 9:30) for the two to meet

61. jim_thompson5910

and for the two to travel the same distance

62. jim_thompson5910

convert to minutes to get: 0.444*60 = 26.64 so it will take about 26.64 minutes

63. gianarpt

thank you very much for helping me i wish i was as smart as you i struggle just to keep my B- average

64. jim_thompson5910

I'm sure you'll do fine, just keep your head up and keep practicing

65. gianarpt

thank you jim have a nice day!

66. jim_thompson5910

you're welcome

67. jim_thompson5910

you too