# Rounding

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## Rounding

Often you are asked to write an answer to a given number of decimal places (be careful to read the question properly!).

**What you need to do:**

**1.** Count the number of decimal places you need.

**2.** Look at the next digit. If it's 4 or below just write down the answer with the right amount of decimal places. If it's 5 or above write down the number but put your last decimal place up by one.

* For example:* 2.3635 to

**two**decimal places

* For example:* 53.586 to

**two**decimal places

**What if the last digit is a 9?**

A 9 goes up to a 10 so you need to put a zero in the last column and add one to the previous number.

* For example:*
8.6397 to

**three**decimal places

**Try this one! Type in what you think the answer is and click the button to see whether you are right:**

**Tips!**

If you are not told how many places to write just **be sensible!** Generally, you should go to one more place than the numbers used in the question.

With angles, no more than **one** decimal place should be used unless told otherwise.

These involve **all** digits, not just decimal places. Zeros are only "significant" if they separate two other non-zero digits!

**What you need to do:**

**1.** Start counting at the **first** non-zero digit until you have the number of digits that you need.

**2.** Look at the next digit. If it's a 4 or below just write the number down leaving the last digit the same. If it's a 5 or above put the last digit up by one.

**3.** If you are rounding **whole numbers** (i.e. to the **left** of the decimal point) put zeros in all the other columns after your last digit until you reach the decimal point.

e.g. 12 736 to **three **significant figures is 12 700

e.g. 6530 to **one** significant figure is 7000

e.g. 0.576 to **two** significant figures is 0.58

**Try this one! Type in the answer and click the button to see if you are right:**

**Tip!**

In real situations, use common sense to decide on your accuracy. E.g. Length of a back garden would not be written as 8.5632 metres. It would be more sensible to write 8.6 metres!