1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Ratio Problem

  1. May 30, 2014 #1
    Hi all

    I have a ratio problem which i was hoping someone could help with.

    The question is this:-

    Barry bough a box full of fruit. The contained some apples, oranges and lemons in the ratio 5:3:1. Given that there were more than 50 pieces of fruit in the box work out the minimum number of oranges in the box.

    I do the following:-



    You cannot have 0.666 of an orange the answer is 17.

    But this is wrong the answer is in fact 18 according to the answer sheet but WHY???

    I know it has something to do with the statement "more than 50 pieces" but i cannot figure it out.

    Can someone help
  2. jcsd
  3. May 30, 2014 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Assume there are N pieces of fruit altogether. How many pieces of each type would there be?
  4. May 30, 2014 #3
    If you were to have 5 apples, 3 oranges and one lemon, you would have 9 fruit.
    So, you can only have n * 9 fruits where n is a positive integer.
    Can you work out the smallest value for n such that n * 9 > 50?
    What does that tell you about the minimum number of oranges?
  5. May 30, 2014 #4


    User Avatar
    Science Advisor

    Another, more "algebraic" way to do this is to let "x" be the number of lemons. Then the number of oranges is 3x and the number of apples is 5x. The total number is x+ 3x+ 5x= 9x so the number of fruit must be a multiple of 9. The smallest multiple of 9 larger than 5 is (9)(6)= 54.
  6. May 30, 2014 #5
    The answer is 6, so 6 * 3 = 18. got it thanks
  7. May 30, 2014 #6
    Past Exam Questions on Ratio

    Hi i found a past exam ratio questions on line and attempted to do them, i have attached my results, can anyone spot any mistakes?


    Attached Files:

  8. May 30, 2014 #7
    First, no the answer is not 6. The answer is 18. Try not to take x for the ANSWER whenever you solve for x.

    Second, I think you should open another topic to place that PDF.

    Third, question 17 is correct to me.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted