What is rounding up?

Some decimal numbers go on for ever! To simplify their use, we decide on a cut off point and “round” them up or down.

If we want to round 2.734216 to two decimal places, we look at the number in the third place after the decimal, in this case, 4. If the number is 0, 1, 2, 3 or 4, we leave the last figure before the cut off as it is. If the number is 5, 6, 7, 8 or 9 we “round up” the last figure before the cut off by one. 2.734216 therefore becomes 2.73 when rounded to two decimal places.

If we are rounding to two decimal places, we leave 2 numbers to the right of the decimal.
If we are rounding to two significant figures, we leave two numbers, whether they are decimals or not.

Rounding up should only be done at the final stage of your calculation. Rounding up midway through can throw out the final result!

Examples:

243.7684 = 243.77 (two decimal places) or 240 (two siginificant figures)

1973.285 = 1973.29 (two decimal places) or 2000 (two siginificant figures)

2.4689 = 2.47 (two decimal places) or 2.5 (two siginificant figures)

0.99879 = 1.00 (two decimal places) or 1.0 (two significant figures)