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countonme123

  • 2 years ago

One man starts out from a city and walks north at the rate of 3 kilometers per hour. Three hours later, a second man starts from the same place and walks the same route at 4 kilometers per hour. How far will he have to go before he overtakes the first man?

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  1. lgbasallote
    • 2 years ago
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    let t = man A's time t + 3 = man B's time when he overtakes the guy they would be at the same distance from the starting point d = speed x time d of man A = 3t d of man B = 4(t-1) like i said if they overtake then distances are the same 3t = 4(t-1) solve for t

  2. lgbasallote
    • 2 years ago
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    oops i did something wrong idk why

  3. lgbasallote
    • 2 years ago
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    d of man B = 4(t+3) like i said if they overtake then distances are the same 3t = 4(t+3) solve for t

  4. lgbasallote
    • 2 years ago
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    @ganeshie8 did i do it right? im smelling negative time -_-

  5. countonme123
    • 2 years ago
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    hmmm im not getting you

  6. countonme123
    • 2 years ago
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    @ganeshie8 do you understand this one? i need your help.

  7. ganeshie8
    • 2 years ago
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    4t-9 = 3t solve for t

  8. lgbasallote
    • 2 years ago
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    9?

  9. ganeshie8
    • 2 years ago
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    wait.. checking im also haunted by -ves... lol

  10. countonme123
    • 2 years ago
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    yes 9 there but then what? and to be honest i dont understand why you arranged that as you did...

  11. lgbasallote
    • 2 years ago
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    lol =))) traumatized :))

  12. countonme123
    • 2 years ago
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    haunted???traumatized??? what are yall talking about?

  13. ganeshie8
    • 2 years ago
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    ok.. you unerstand straight lines in slope-intercept form ?

  14. countonme123
    • 2 years ago
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    dont think so

  15. countonme123
    • 2 years ago
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    you still working on it?

  16. ganeshie8
    • 2 years ago
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    ok.. as @lgbasallote said, distance is same here right. distance travelled by First man in time t = 3t in 3 hours he would have travelled 9 km so 9km is the distance second man lags when he starts his run. he is running at 4t speed. so at any point he will be covering (4t-9km) distance so far does it make sense ?

  17. countonme123
    • 2 years ago
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    yes

  18. countonme123
    • 2 years ago
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    please continue

  19. ganeshie8
    • 2 years ago
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    so, now we can equate the distance and get the value of t. distance travelled by first man : 3t distance travelled by second man : 4t-9 4t-9 = 3t => t = 9 hours so, after 9 hours, both guys would have travelled the same distance. but question is asking about the distance second man has to travel before he overtakes first man, right ?

  20. countonme123
    • 2 years ago
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    yah

  21. saranya
    • 2 years ago
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    You can do this in two ways, do it in one way and check it using the second way. The first is to use the speed/distance/time formula and the second is to use a velocity-time graph and use the areas.

  22. vishweshshrimali5
    • 2 years ago
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    I can surely help What we have to do is just to use the concept of relative velocity

  23. vishweshshrimali5
    • 2 years ago
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    FIrst of all, Find out what distance does first person travel in those 3 hours

  24. vishweshshrimali5
    • 2 years ago
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    Now second person has to travel this distance + some more distance. Now relative velocity of second person wrt first person = 4-3 km/h = 1 km/h Now he has to travel a distance equal to distance travelled by first person in 3 h and that also with a relative speed of 1 km/h. From here find out the time

  25. countonme123
    • 2 years ago
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    hmm confusing

  26. vishweshshrimali5
    • 2 years ago
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    u start solving step by step . I am here to help u

  27. countonme123
    • 2 years ago
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    ok well all i know is 3k per hour and 3 hours later equals a 9kmperhour advantage.

  28. vishweshshrimali5
    • 2 years ago
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    Only 9 km advantage in this 3 hour interval. Now use the concept of relative velocity First person let A is moving with 3 km/h Second person say B is moving with 4 km/h So B has an advantage of 1 km/h Right ? This is the relative velocity of B w.r.t A

  29. vishweshshrimali5
    • 2 years ago
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    Got this ?

  30. countonme123
    • 2 years ago
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    yes he can over take him because he goes a bit faster got that

  31. vishweshshrimali5
    • 2 years ago
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    Yes gud Now overall B has to travel 9 km at a speed of 1 km/h Right, I am taking relative speed here as that will help me in assuming that A is at rest. Now, time taken by B to travel these 9 km = 9 h Got this ?

  32. countonme123
    • 2 years ago
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    yes to eliminate that advantage

  33. vishweshshrimali5
    • 2 years ago
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    Now what distance B actually travelled during these 9 hours = 9 * 4 = 36 km

  34. vishweshshrimali5
    • 2 years ago
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    I hope I did that correctly ?

  35. countonme123
    • 2 years ago
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    then the other guy went 9x3 = 27 + the 9 advantage =36 so they both tie at 36?

  36. vishweshshrimali5
    • 2 years ago
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    Of course

  37. countonme123
    • 2 years ago
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    but a tie is not an overtake

  38. vishweshshrimali5
    • 2 years ago
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    It is not that dear, If you have tied it than it will not even take a second for B to overtake A as he has an advantage of 1 km/h speed so that wouldn't be right to tell when B will overtake

  39. countonme123
    • 2 years ago
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    wouldnt?

  40. vishweshshrimali5
    • 2 years ago
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    Yes ofcourse

  41. countonme123
    • 2 years ago
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    hmm i think i lost you

  42. vishweshshrimali5
    • 2 years ago
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    What happened

  43. countonme123
    • 2 years ago
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    i dont get the tie/overtake thing

  44. vishweshshrimali5
    • 2 years ago
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    See If I say u that me and u r having a race I was ahead of u when u started but u started with a higher speed A time came when I and U were at same point but as you are having more speed than me U will easily overtake me even without taking a second after the tie point Got this ? So, that's why in such case we calculate the tie point as obviouslly after a very small time u will be ahead of me

  45. countonme123
    • 2 years ago
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    hmm but to be technical the the answer would be a tiny bit over 36

  46. vishweshshrimali5
    • 2 years ago
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    Yes but that tiny but will be very very very close to 0

  47. countonme123
    • 2 years ago
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    yes i see so 36 then

  48. vishweshshrimali5
    • 2 years ago
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    yes

  49. vishweshshrimali5
    • 2 years ago
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    did that help u ?

  50. countonme123
    • 2 years ago
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    yes very much thank you i may message you one like this but a bit harder

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