Arithmetic : Decimals

Preparation

Just what you need to know !

Addition and Subtraction of Decimals

To add or subtract decimals,

write the decimals one below the other such that the decimal points are vertically aligned;
insert zeros to the right of the decimal fraction to fill any gaps so that all numbers have same number of digits to the right of the decimal point;
add or subtract the numbers in the same way as whole numbers (ignoring the decimal point); and
insert a decimal point in the result directly under the decimal points of the numbers added or subtracted.

Example
The separate weights in grams of four gold rings are 3.012, 5.6, 4.89 and 6. How much do the four rings weigh altogether?
Solution.

The four rings altogether weigh 19.502 grams.

Example
Rebecca has $87. If she spends $9.56, how much money does she have left?
Solution.

						  87.00
			-  9.56
			77.44

Rebecca has $77.44 left.
Note that subtraction may be always verified by addition, e.g., 77.44 + 9.56 = 87.