The Magic & Joy of Exploding Dots: A revolutionary concept that changes the way we learn and teach mathematics by Bacche Kiran & Tanton James & Propp James

Author:Bacche, Kiran & Tanton, James & Propp, James [Bacche, Kiran]
Language: eng
Format: epub
Publisher: White Falcon Publishing
Published: 2020-07-06T16:00:00+00:00

With explosions, this becomes 18.305. (Check this!)

We can also explain a rule that students are taught to memorize:

If you multiply a decimal by 10 , just shift the decimal point one place to the right.

For example, 31.42 × 10 gives the answer 30 | 10 . 40 | 20. With explosions, this becomes 314.20 and the answer looks as though we just shifted the decimal point. (Most people leave off the final zero.)

By the way, if you multiply a number a little larger than 31 by ten, you should get an answer a little larger than 310. Memorizing the direction of travel of a decimal point is unnecessary.

13. Explain why multiplying a decimal by 100 has the same effect as shifting the decimal point two places? (Do you need to memorize the direction of the shift?)

We can also multiply decimals by decimals, but now the work is getting less fun. We need to follow the same approach as we did when we explored long multiplication in chapter 3.

Let’s do an example. Consider 2.15 × 0.3.

Here’s what 2.15 looks like.

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