Thursday, November 13, 2014

Math POTW #9 - Mmmmm Pizza

Please see the last week's POTW (#8) replies for the correct response to the question. This week's question is:

10 comments:

  1. I made a chart to see what the cost would be originally to thee number of students there could have been.
    10 kids: 14.40/10=1.44 7 kids: 14.40/7=2.05 2.05-0.40=1.65
    12 kids: 14.40/12=1.20 9 kids: 14.40/9=1.60 1.60-0.40=1.20 <-- Correct Answer

    After my second try, I found out that there are 12 kids who supposedly paying 1.20 each but since 3 kids forgot their money, 12-3 is 9 which results in having each of the 9 kids pay 1.60. In the question, it states that each of the other kids, had to pay extra 40 cents so 1.20 + 0.40 is 1.60. Therefore, 12 students were originally supposed to pay for the pizza.

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  2. 10 people = $1.44 each. $1.44 x 3 = $4.32. $4.32/$0.40 = 10.8 not 7 (the 7 others who had money)
    12 people = $1.20 each. $1.20 x 3 = $3.60. $3.60/$0.40 = 9 (9 others who had money)
    There were originally 12 people who were supposed to pay.

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  3. To find the answer i had to find 14.4÷X x 3 ÷ 0.4= X-3
    X is the amount of people who were willing to pay.
    so i used guess and check, starting with 10 as it is easy to divide a decimal by 10.
    14.4÷10=1.44, 1.44x3= 4.32, 4.32 ÷ 0.4= 10.8 10-3=7 X
    14.4÷11=1.31, 1.31x3= 3.93, 3.93 ÷ 0.4= 9.825 11-3=8 X
    14.4÷12=1.20, 1.2x3=3.6, 3.6 ÷ 0.4 = 9, 12-3= 9 V
    Therefore i know that in the beginning, there were 3 students who were willing to pay

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    Replies
    1. I don't understand???

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    2. I don't think that only 3 students were willing to pay. In the question, it says that 3 people forgot their money, but the bill was paid. If all 3 people forgot their money, they couldn't have paid the bill.
      Can you please explain what you did?

      Delete
  4. X=students, Y=original cost per one student
    Formula: 14.40/X=Y. 14.40-(Yx3)=Z. Z+(X-3)x0.40=14.40

    First I tried testing out logical numbers starting from 14.
    14.40/14=each student should pay around 1.03. 14.40-(1.03x3)=11.34. 11.34+(11x0.40)=15.74 which is over the cost, I now need to repeat the formula with different numbers.
    14.40/12=1.20. 14.40-1.20x3=10.8. 10.8+9x0.40=3.6. 10.8+3.6=14.40. There were 12 students originally going to pay for the pizza

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  5. To find the answer I did guess and check:
    10 students: $1.44 per person. $1.84 for 7 people=$12.88. $12.88<$14.40 so we have to add more people
    12 students: $1.20 per person. $1.60 for 9 people=$14.40. $14.40=$14.40 so there were 12 people

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  6. I did guess and check. I knew what I had to do(formula) but I didnt know the amount of people so I just wrote an algebraic expression which is: 14.40÷a=b 14.40-(bx3)=c c+(a-3)x0.40=14.40
    I started with 10.
    14.40÷10=1.44 14.40-(1.44x3)=10.08 10.08+(10-3)x0.40=12.88
    I was a little short so I tried 11.
    14.40÷11=1.31 14.40-(1.31x3)=10.47 10.47+(11-3)x0.40=13.67
    Next I tried 12 and I knew it would work since the last time it raised by about a dollar and I need about a dollar more.
    14.40÷12=1.2 14.40-(1.2x3)=10.8 10.8+(12-3)x0.40=14.4= correct answer
    The correct answer is 12 students were originally going to pay.

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  7. Wow, lots of students obtained the correct answer for this week's POTW! There were 12 students who originally agreed to pay for the pizza (9 students only ended up paying in the end though).

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  8. I tried and made a chart, but my correct result was
    12 kids: 14.40/12=1.20 9 kids: 14.40/9=1.60 1.60-0.40=1.20
    There were 12 kids

    ReplyDelete