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anonymous

  • 5 years ago

Jack can do a job in 2 hours, Tom in 5. Can someone verify the answer isn't one of the choices?

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  1. anonymous
    • 5 years ago
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  2. anonymous
    • 5 years ago
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    x x -- + -- = 1 2 5 Multiply every term by 10 5x + 2x = 10 7x = 10 x = 10/7 x = 1 and 3/7 of an hour.

  3. anonymous
    • 5 years ago
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    but 7 isnt a common denominator?

  4. anonymous
    • 5 years ago
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    @Blexting - could you explain? this isn't AOPS where everyone understands.

  5. anonymous
    • 5 years ago
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    isn't 1/2 + 1/5 = 3/10?

  6. anonymous
    • 5 years ago
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    i mean 7/10 oops

  7. anonymous
    • 5 years ago
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    OHH i see what i did wrong

  8. anonymous
    • 5 years ago
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    i simplified but forgot to use the reciprocal denominator :P damnit

  9. anonymous
    • 5 years ago
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    sorry, & thanks

  10. anonymous
    • 5 years ago
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    x is the number of hours someone works. Take Tom... in 1 hour he has done 1/5 of the job.. in 2 hours he has done 2/5 of the job... in 3 hours 3/5 of the job. We want the job to add to 1 because then you have done "let's say 5/5" of the job which is the whole job. in 1 hour jack would do 1/2 of the job and Tom 1/5 of the job. which would be 7/10 of the job. in 2 hours jack would do 2/2 of the job and Tom 2/5 of the job.. which would be 1 2/5.. (Jack would have completed it on his own). These are always setup the same way x over (how long it takes for one person) + x over (how long it takes for the other person) = 1

  11. anonymous
    • 5 years ago
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    Hrm. Never saw it that way. I just always thought of it through rates, and then just brute forced it. qq

  12. amistre64
    • 5 years ago
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    1/2 + 1/5 = 7/10 7 parts get done in 1 hour, and there are a total of 10 parts to do. after 1 hour, there are still 3 parts to finish up. 60 minutes/7 times 3 = how many minutes?

  13. amistre64
    • 5 years ago
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    180/7 = 25.7 is close... 1 hour 25 minutes and a few seconds...

  14. anonymous
    • 5 years ago
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    I left it 1 3/7 hours because it matched the multiple choice he was picking from.

  15. amistre64
    • 5 years ago
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    thats a good option as well :)

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