MathMaster Blog

Rounding a number means simplifying it while retaining its value close to what it was.

First, you need to comprehend the rounding digit concept:

when working with whole numbers and rounding to the closest 10, the ​rounding digit is the second number on the right — or the 10's place;

when rounding to the nearest hundred, the third place on the right is the rounding digit — or the 100's place.

The general rule for rounding numbers:

• Step 1: Choose the final digit to keep;
• Step 2: If the following digit is less than 5, keep it the same (rounding down);
• Step 3: If the next digit is 5 or more, raise it by one (rounding up);

Rounding decimals

When rounding to tenths, leave one number after the decimal point.

When rounding to the hundredths, leave two digits after the decimal point, etc.

Rounding to whole numbers

If you need to round to tens, hundreds, etc., the first thing to do is to replace the removed digits with zero.

Rounding to significant digits

Count the digits from left to right, then round off.

Example 1:

Round 74 to the nearest 10.

Solution:

Step1:

We want to keep the ‘7’ (it is in the 10s position);

Step2:

The next digit is ‘4’ which is less than 5, so no change is needed for ‘7’;

Answer: 70 (74 gets rounded down)

Example 2:

Round 86 to the nearest 10.

Solution:

We want to keep the “8”. The next digit is “6” which is 5 or more.

Answer: 90 (86 gets rounded up)