Fractions &
Decimals:
Lazy Loops
Today's
Snack: Since
we're going to be drawing lazy little loops that look like Spaghetti-O's, why
not have a bowl of that kid-pleasing pasta? Enjoy a glass of grape juice with
it.
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Supplies:
Cardboard or cardstock
Yarn in 2 colors | Scissors | Tiny
yarn pompom | Glue
Here's a 3-D way to master the math "trick of the
trade" for multiplying a decimal by 10, 100, 1,000 and so on.
First, using yarn, a tiny yarn pompom, and glue, cut
out the shapes to make this number or a similar one on a sturdy piece of
cardboard or cardstock. Use the pompom as the decimal point. Glue it in place:
7.58926
Now, using the other color of yarn, and your
fingers, make a "lazy loop" underneath. Form it after the decimal point, to
show where the decimal point will move if you multiply that number by 10.
In that example, the lazy loop will start at the
decimal point, loop under the five, and end between the 5 and the 8 - where the
new decimal point would be if you multiplied 7.589 x 10.
What if you multiplied that number by 100? Then you
would have to make two lazy loops - one from the existing decimal point,
looping underneath to end between the 5 and the 8, and the second looping from
that point to between the 8 and 9.
That is where the new decimal point would be if you
multiplied that number x 100.
Play around with 1,000, 10,000 and 100,000, too.
Then choose 10, 100, 1,000, 10,000 or 100,000. Write
it after the number, like this:
7.58926 x 1,000
Carefully glue lazy loops from the existing decimal
point to wherever the new decimal point would be if you multiplied by that
number.
In this case, you would have loops from the existing
decimal point underneath to between the 5 and the 8, another one underneath
that spot to between the 8 and the 9, and a third loop underneath that spot to
beneath the 9 and the 2.
Pull up the tiny pompom that you were using as your
decimal point, and re-glue it in place between the 9 and the 2.
Then write the equation underneath:
7.58926 x 1,000 = 7,589.26
