• n0m4n@lemmy.ml
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        1 year ago

        Which equals 29^2 x .01 => ((28 x 30) +1) X .01
        => (840 + 1) x .01 => 8.41

        28 x 30 is an easy mental calculation, as is adding 1, as is moving the decimal place over 2 places. I am teaching this to 4th graders, in two weeks. % to decimal is next week. They can square 2-digit numbers in their heads, already.

    • Sludgeyy@lemmy.world
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      1 year ago

      1% of 33 is .33

      .33 × 7 =

      .3 x 7 = 2.1

      .03 x 7 = .21

      21 + 2.1 = 2.31

      So

      7% of 33 = 2.31

      You could also do

      33% of 7

      10% of 7 is .7

      1% of 7 is .07

      So 11% is .77

      .77 × 3 =

      .7 × 3 = 2.1

      .07 × 3 = .21

      2.1 + .21 = 2.31