13 thoughts on “Maths Is Hard

  1. Tsquared – Yeah, me, too.
    16 is about 1/6 of 100 (6 X 16 = 96) so unless you want fractions, 1/6 of 25 = 4. (24/6 = 4). The other way to do it is 10% + 6%….10% of 25 = .1X 25, = 2.5, just move the decimal over 1 place; 6% of 25 = .6X2 + .6X5 which is 1.2 + .3 which is 1.5 + the original 2.5 = 4. (Actually, it’s .6X20/100 because the goal is 6% which is expressed as .06 because percentage is 100.

    What looks like a large complex problem can be broken down into simpler parts. 18 X 44 = 10 X 44 (440) + 8 X 40 (320) + 8 X 4 (32) and 440 + 320 (760) + 32 = 792.

    Or, just 20 X 44 (880) – 88 = 792. 20 X 44 is 2 X 44 plus the hundreds zero (88 + the 0 = 880 – it’s just a decimal place move, one notch to the right) 2 X 44 = 88 and 88 is 12 less than 100 so subtract 100 from 880 (780) and add back the 12 (792).

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    • I saw it as 25 x .16 = 4 I subscribe to the KISS formulas in math.

      My mind is wired that way. Out to 4 digits I got the answer immediately with simple multiplication and division but, adding and subtracting I can carry out to 6 or 7 digits. I have to think a little more with more digits and more complex formulas.

      When I was younger and I would meet somebody new where they would introduce themselves I would ask them the last 6 digits of their SS#. A few weeks later I would see them again and I remembered the last 6 of the SS# but had no clue what their name was. I used it as a party trick when I was in college.

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  2. If the problem was expressed in a math formula style the answer would be obvious. forget the decimal point. 16 x 25 = 400 move the decimal point two places to the left….4

    It is how the question is asked that makes it hard and not the actual math.

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  3. They probably taught you but just didn’t teach you where to use it. It’s just the Associative Property of Multiplication. So (a*b)*c=a*(b*c). 16% is also 16*(1/100) therefore (16*(1/100))*25 is the same as 16*((1/100)*25.

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  4. This is perfect timing! I’ve been teaching my 11 y/o percentages and fractions the past few weeks. She only listens to Dad so much. This is a great video to help explain to her what she doesn’t want to hear from me!

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  5. I usually break the problem down to the tens and ones digits. The tens is easy, shift the decimal. The ones is slightly harder. Add the two, and you’re there.
    But I gotta admit, the way we were just shown is a whole lot faster.

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  6. I really suck at math, always have and resigned myself that’s the way it always will be. It’s not that math is all that hard, it’s just that the way it’s taught don’t make a lick of sense to a lot of people.
    Thankfully my math books were the same size as my car magazines, cause I sure learned a lot about cars & engines and all that stuff during math class….

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  7. .16 x 25= 16 x 25 divided by 100

    So, 16 x 25 = 4x4x5x5 equals 4 x 5 times 4×5

    So 20 times 20 is 400. Then divide by 100 for the quotient 4

    So easy my 4th graders showed me how to do it.

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