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Math Help - Help with pattern to numbers and average speed.

  1. #1
    Senior Member Mukilab's Avatar
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    Help with pattern to numbers and average speed.

    if nyone cn plese do this s fst s possible.





    What should be the value of the fourth column?



    oh and
    Rudolph travels at 993 mph on Christmas Eve in order to deliver presents to all the children.

    He returns home, over exactly the same distance, at 331 mph.


    What is his average speed over the entire journey?




    i got p to 662= \frac{D}{T}
    Last edited by mr fantastic; December 12th 2009 at 01:30 AM. Reason: Merged posts, changed post title
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  2. #2
    Super Member 11rdc11's Avatar
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    Quote Originally Posted by Mukilab View Post
    if nyone cn plese do this s fst s possible.





    What should be the value of the fourth column?
    Is the correct answer 73?
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  3. #3
    Senior Member Mukilab's Avatar
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    Quote Originally Posted by 11rdc11 View Post
    Is the correct answer 73?
    yes, plese show your working

    the nswer for the second one is 496.5
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  4. #4
    Super Member 11rdc11's Avatar
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    Quote Originally Posted by Mukilab View Post
    yes, plese show your working

    the nswer for the second one is 496.5
    I assigned a variable to each color

    a= red
    b=yellow
    c=blue

    Now make three equations with the given

    a + 2b +c = 78
    2a + b + c = 77
    3a +b = 81

    Now solve these equations by elimnation.

    Then plug the values you found for a,b,c into the equation for the final line

    a + b + 2c = ?
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  5. #5
    Senior Member Mukilab's Avatar
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    yes, sorry, i calmed down a bit after posting and was able to work it out with ease. any answers to my second query?

    I used substitution though
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  6. #6
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    Quote Originally Posted by Mukilab View Post
    [snip]
    Rudolph travels at 993 mph on Christmas Eve in order to deliver presents to all the children.

    He returns home, over exactly the same distance, at 331 mph.


    What is his average speed over the entire journey?

    i got p to 662= \frac{D}{T}
    Let distance each way be x.

    Then t = (x/993) + (x/331) = (4x)/993.

    Then average speed = (2x)/[(4x)/993] = 993/2 mph.
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  7. #7
    Senior Member Mukilab's Avatar
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    Quote Originally Posted by mr fantastic View Post
    Let distance each way be x.

    Then t = (x/993) + (x/331) = (4x)/993.

    Then average speed = (2x)/[(4x)/993] = 993/2 mph.
    how did you keep the 993 there?

    I'm assuming you accounted for the 2 distances and two times to get 4x...
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  8. #8
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    Quote Originally Posted by Mukilab View Post
    how did you keep the 993 there?

    I'm assuming you accounted for the 2 distances and two times to get 4x...
    993 is the common denominator for the total time of the trip. You should know that average speed = distance/time. Distance is 2x. Time is as calculated.
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  9. #9
    Senior Member Mukilab's Avatar
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    what would be the common denominator for 33.3 recrring and 50?
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  10. #10
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    Quote Originally Posted by Mukilab View Post
    what would be the common denominator for 33.3 recrring and 50?
    What has this got to do with the original question? Post new questions in a new thread. (This question belongs in Pre-algebra).
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  11. #11
    Senior Member Mukilab's Avatar
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    Quote Originally Posted by mr fantastic View Post
    What has this got to do with the original question? Post new questions in a new thread. (This question belongs in Pre-algebra).
    the same question basically
    A delivery lorry covers its outward journey at 50mph.

    It returns, over exactly the same distance at 33.3333mph.

    What is the lorry’s average speed over the entire journey?
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  12. #12
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    Quote Originally Posted by Mukilab View Post
    the same question basically
    A delivery lorry covers its outward journey at 50mph.

    It returns, over exactly the same distance at 33.3333mph.

    What is the lorry’s average speed over the entire journey?
    You have been shown in detail how to do this sort of question. The only thing different are the numbers. You're expected to learn something from the help you get. Use a calculator if you cannot do the basic arithmetic.

    Thread closed.
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