A decimal is a number that includes a decimal point, which separates the whole number part from the fractional part. For example, 3.14 is a decimal.

To add decimals, align the numbers by the decimal point and add as you would with whole numbers, placing the decimal point in the sum directly below the other decimal points.

'Altogether' means to find the total amount by adding numbers together.

To find the difference, align the numbers by the decimal point and subtract as you would with whole numbers.

Estimating helps to quickly find an approximate answer, which can be useful for checking the reasonableness of a calculated answer.

'Faster' refers to completing a task in less time compared to someone else.

To round a decimal, look at the digit to the right of the decimal point. If it's 5 or more, round up; if it's less than 5, round down.