Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Need Help Immediatly

  1. Oct 16, 2004 #1
    I Need Help Immediatly!!

    I have another stupid algebra story problem that is really hard for me and might be easy for others. If you come up with the answer please tell me, or give me clues on how to figure the problem out. The teacher is asking for an explanation to go with the answer to! DUE MONDAY!

    Big Jesse takes 2 steps for every 3 steps that Little Jesse takes. To bein walking, they each step forward on their right foot at exactly the same time. When will their left feet touch the ground at exactly the same time??
  2. jcsd
  3. Oct 16, 2004 #2
    While I can't tell you the answer directly, forum rules, I'll try and put you on the right track. If you start with your right foot, the only way you'll end up with your left foot forward is if you take an even number of steps. So the question is really, "At what point will Big Jesse and Little Jesse both have taken an even number of steps?" At any given time, Little Jesse has taken 1.5 times as many steps as Big Jesse. See if you can write an algebra equation that, when solved for the variable, will equal the smallest even number that results in another even number when multiplied by 1.5. What does this number represent? What does this number times 1.5 represent? Hope that helps.
  4. Oct 16, 2004 #3
    i am still really confused, i am only in 7th grade
  5. Oct 16, 2004 #4
    Hmm...perhaps it would help if you figured out the answer some other way first and then came up with an algebra equation, if that's what your teacher said you need. This problem is simple enough that it doesn't require algebra to solve. If you still can't figure the problem out without using an algebraic equation, see if you can come up with a real life model of the problem- maybe ask your parents to play Big Jesse and Little Jesse, and have one take 1.5 steps for every 1 step the other takes (this is the same as saying 3 steps for every 2 the other takes). Count the number of steps each takes before both have their left foot forward. With the answer in hand, maybe you'll have an easier time coming up with an equation.
  6. Oct 19, 2004 #5
    2:3 ratio

    Just put on paper LR LR L

    and write your equation from that.
  7. Oct 20, 2004 #6


    User Avatar
    Science Advisor
    Homework Helper

    It's like playing the piano: Eight triplets vs. Quarters. But with added left and right:
  8. Oct 20, 2004 #7
    {For every step A takes B takes 1,5
    {their first step was at the same time
    {their first step was with the right foot

    If they both start at the same time, steps(B) = 1,5*steps(A) - .5, cause A(1) = B(1)

    Every second step for A is a left step, and every second step for B is a left step. The question is thereby:

    When is 2x = 1,5*2n - .5?

    Last edited: Oct 20, 2004
  9. Oct 20, 2004 #8
    [The Above is a visual aid for me and others, it seperates the steps into twos and threes with eqaul signs]

    I believe it is impossible for them to both step with their left feet at the same time. I believe this because of what Galileo said about triplets and quavers in music. As the person, who takes two steps compared to the others three, always steps on the right foot. This is the only time that they can step together as the other steps are at different times.

    The Bob (2004 ©)
  10. Oct 21, 2004 #9


    User Avatar
    Science Advisor

    What is the smallest number that is divisible by both 2 and 3?
  11. Oct 21, 2004 #10
    But HallsofIvy, they take the first step simultaneously with the right foot. Adding to this that Little Jesse takes 1.5 steps for every step Big Jesse takes, we get step(Little Jesse) = (3/2)step(Big Jesse) - 1/2

    Both step(Little Jesse) and step(Big Jesse) must be even, and that never happens.
    Last edited: Oct 21, 2004
  12. Oct 21, 2004 #11


    User Avatar
    Science Advisor
    Homework Helper

    True. After 6 steps they set their foot down simultaneously for the first time after the first step, but it's their right foot, so the process repeats from there.
  13. Oct 21, 2004 #12
    If Big Jesse takes 2 steps for every 3 steps that Little Jesse takes, Little Jesse takes 1.5 steps for every step Big Jesse takes,
    steps(Little Jesse) is proportional to 1.5*steps(Big Jesse) + C.

    If they both step the first step simultaneously
    steps(Little Jesse) = 1.5*steps(Big Jesse) -.5

    If steps(Big Jesse) is even Big Jesse steps with his left foot and 1.5*steps(Big Jesse) -.5 is X.5

    Can we all agree on this Galileo?
    Last edited: Oct 21, 2004
  14. Oct 21, 2004 #13


    User Avatar
    Science Advisor
    Homework Helper

    Think about it this way:

    Both people are on their right foot.
    Person one takes 2 steps (back to right)
    Person two takes 3 steps (to left)
    This is the first time they hit simultaneously.

    You can tell person two goes between right and left, while person one is ALWAYS right when they hit together.

    So they never hit their left feet together.
  15. Oct 21, 2004 #14
    I have already said this. Why do people not listen??? :grumpy:

    The Bob (2004 ©)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook