Thursday, November 15, 2018

POTW #11 - We need more submissions!

Please don't forget to do these POTWs each week! I have noticed a drop-off in student participation.

POTW #10 Solution:

POTW #11 Question:



13 comments:

  1. Grade 7/8 POTW
    We also did this one last year, but I'll do it again. First, let's list the facts. Note* I already made the sums and the variables that add up to them:
    - a<b<c
    - a + b = 2986
    - a + c = 3464
    - b + c = 3550
    I'm just going to go straight into the math.
    (a+c) - (a+b) = c - b = 3464 - 2986 = 478
    (b+c) - (b+a) = c - a = 3550 - 2986 = 564
    (c+b) - (c+a) = b - a = 3550 - 3464 = 86
    Therefore:
    c = b + 478
    c = a + 564
    b = a + 86
    b = c - 478
    a = c - 564
    etc (many equations can be formed)
    We can now use substitution and algebra to solve.
    a:
    2986 = a + (a + 86)
    2986 = 2a + 86
    2986 - 86 = 2a
    2900 = 2a
    1450 = a
    b:
    3550 = b + (b + 478
    3550 = 2b + 478
    3550 - 478 = 2b
    3072 = 2b
    1536 = b
    c:
    3464 = c + (c - 564)
    3464 = 2c - 564
    3464 + 564 = 2c
    4028 = 2c
    2014 = c
    a = 1450
    b = 1536
    c = 2014
    To double-check with the actual values, we can simply just plug in the values into the equation.
    a + b = 1450 + 1536 = 2986
    a + c = 1450 + 2014 = 3464
    b + c = 1536 + 2014 = 3550
    Therefore, the value of the largest value is 2014.

    ReplyDelete
    Replies
    1. If you're in Grade 8 then you might see a trend here. Not every week of course. And yes, do them again if it is the case!

      Delete
  2. Grade 7/8 POTW:
    Info a<b<c
    When added, gives 2986, 3464 and 3550

    Using common sense, I know that because of larger and smaller numbers, the following equations must be true.
    a+b=2986
    a+c=3464
    b+c=3550

    The question is basically asking “what is the largest possible value for c. We need a to be big, but not too big because we need b to be small, so c can be large. a has to be a large number but small enough to be smaller than b. To find a possibility, we can divide the same 2986 by 2 and make a one smaller than the quotient. 2986/2=1493. 1493-1=1492.
    a=1492
    b=1494
    c= 3550-1494= 2056

    This is the largest possible value for the largest number. (If I did anything wrong, I’ll fix any errors).

    ReplyDelete
  3. We can try to combine all three equations into one larger equation:
    (a+b)+(b+c)+(a+c)=2986+3464+3550 (Since this is addition, we can open the brackets)
    2a+2b+2c=10000 (Factor out the common factor)
    2(a+b+c)=10000
    a+b+c=5000

    To find c, we can take what we know about the sum of all three numbers and combine that with the equation of a and b.
    (a+b+c)-(a+b)=5000-2986 (Since we are now dealing with subtraction of a bracket, we need to flip the sign from inside the bracket).
    a+b+c+-a-b=2014 (Combine like terms)
    c=2014

    a= 3464-2014
    a=1450

    b=3550-2014
    b=1536

    (therefore) the largest number is 2014.

    Correct me if I’m wrong, but I also remember doing this POTW last year.

    ReplyDelete
    Replies
    1. If you're in Grade 8 then you might see a trend here. Not every week of course.

      Delete
  4. Grade 7/8 POTW
    If B and C are the two largest numbers, then their sum has to be equal to the largest number which is 3550. If A and C are the largest and smallest number, they have to be equal to the second largest number which is 3464. Lastly, A and B are the smallest and middle number meaning that their sum has to be equal to 2986. I will use guess and check to solve this problem and my first guess will correspond with the given amounts that the letters are measured to approximately be.
    After about 2 guesses I was left with the correct answer of
    c=2014
    b=1536
    a=1450
    My first guess was c=2000 and then with this amount, I found out the values of the other letters and concluded that the answer was about 40 off. I then raised and raised the value of C until I came up with 2014 which was the correct value of C. Then, I found out the other values to get my answer.

    The largest number is 2014 and I only found out the other values to check that my answer was correct.



    ReplyDelete
  5. We know that a+b subtracted from a+b+c must equal the value of c. To find this, we need to find out the value of a+b+c, and subtract the simultaneous equations. We know that (a+b) = 2986, (a+c) = 3464 and (b+c)= 3550. Adding these up, we get pais of both a, b, and c. Then, we just subtract.

    2a+2b+2c=2986+3464+3550=10000
    -
    2a+2b=5972
    =
    2c=4028
    c=2014
    Then, we can do the operations to find the value of b and a.
    2014+b=3550
    b=3550-2014
    b=1536
    2014+a=3464
    a=3464-2014
    a=1450
    DOUBLE CHECK
    a+b=2986
    1450+1536=2986 is true

    Therefore, the biggest number is 2014, the smallest number is 1450 and the middle number is 1536.

    ReplyDelete
    Replies
    1. whoops I was sleepy and spelled "pairs" wrong

      Delete

  6. 2986= a+b
    3464= c+a
    3550 = c+b
    2a+2b+2c=2986+3464+3550=10000
    10000=2a+2b+3b
    a+b+c=5000
    5000-2986(a+b)= 2014
    c=2014

    ReplyDelete
  7. Info:
    2986 = a + b
    3464 = c + a
    3550 = c + b

    Math =
    2a + 2b + 2c = 10000 = 2986 + 3464 + 3550

    10000 / 2 = 5000 = a + b + c
    5000 - 2986 (a + b) = 2014

    c = 2014

    ReplyDelete
  8. a+b=smallest=2986
    c+a=middle number=3464
    b+c= the largest=3550
    2986(a+b)+3464(a+c)+3550(b+c)=1000
    2a+2b+2c= 1000
    1000/2= 500
    1000/2= a+b+c
    500=a+b+c
    500-a+b=c
    500-2986=c
    c=2014
    The answer for c is 2014

    ReplyDelete
  9. POTW:

    a + b = 2986
    b + c = 3550
    c + a = 3464

    2986 + 3550 + 3464 = (a+b) + (b+c) + (c+a) = 2a + 2b + 2c = 1000

    1000/2 = 5000

    500-2986 = 2014

    c = 2014

    ReplyDelete
  10. We know that a < b < c, and:
    a + b = 2986 - Equation 1
    a + c = 3464 - Equation 2
    b + c = 3550 - Equation 3
    This means that:
    b + (3464 - a) = 3550 - From equations 2 and 3
    b - a = 3550 - 3464 = 86
    b - a = 86
    b = a + 86
    Now, using Equation 1
    a + (a + 86) = 2986
    2a = 2986 - 86
    Therefore,
    a = 2900 / 2 = 1450
    Now, we know that a = 1450
    Therefore, b = a + 86 = 1450 + 86 = 1536
    We also know that b = 1536
    Finally, 1536 + c = 3550, so 3550 - 1536 = 2014
    We know that c = 2014
    So, 1450 < 1536 < 2014

    ReplyDelete