CTC Math Review: How To Round Off Decimals In Math:

Rounding off decimals in Math in actually much more difficult than you might imagine!

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Decimals are used for many different things, but many to show a percentage of a whole number. For example 2.34. The 34 means that it is 34 out of one whole number.

But decimals can go all the way to billions, trillions, zillions! There is no “end” to how many numbers go on after the little dot which signifies “the decimal”.

6.72847582847528578284710010283757283788283774828374832447 is still a number… technically. Though, I think someone might just round it off to something simply, like 6.728. That’s an easier number!

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But rounding off numbers can’t just be anything random. It needs to be accurate!

For example, let’s use 45.76. Then, we can take that number, and try to round it off as best as we can, to make it a smaller number.

45.76.

OK, let’s round off the .76. We’ll try and round it to a whole number first. 76 is closer to 100 than 0, so we’ll round it off to 46.

But we could also round off just the 76 to one number, instead of dismissing the decimal entirely. To do that, we need to see which tenth it’s closest to. 76 is closer to 80 than 70, so it will be 45.8. The 0’s are deleted, because they don’t really matter at the very end.

The first number after the decimal is the 10th.

The second is the 100th.

The third is the 1000th.

The fourth is the 100,000th.

The fifth is the 1,000,000th.

And so on.

So, if someone says “round the decimal point down to the 100th”, then round it up to have just two numbers left.

We’ll two that in one example:

5.678.

So, we need to have just one left. The hundredth is 7, so we’ll round 78 off. It’s closest to 80, to our final answer is 5.68. We rounded it off to the hundredth, and got rid of one number!

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And that’s how rounding off decimal points works!

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Thanks for reading!