What are the rules for multiplying decimals?

Answer 1

Multiply the numbers without the decimal points.

Count the total number of digits after the decimal point in the original numbers and put the decimal point into the answer so that there are the same number of digits after the decimal point.

Examples:

• 2.4 x 3.24

do 24 x 324 = 7776

There is one digit in 2.4 and two in 3.24 after the decimal points making three digits in total, so insert the decimal point into the answer so that there are three digits after it: 7776 → 7.776

⇒ 2.4 x 3.24 = 7.776

• 2.5 x 3.26

do 25 x 326 = 8150

There is one digit in 2.5 and two in 3.26 after the decimal points making three digits in total, so insert the decimal point into the answer so that there are three digits after it: 8150 → 8.150

⇒ 2.5 x 3.26 = 8.15

• 2.5 x 0.02

do 25 x 2 = 50

There is one digit in 2.5 and two in 0.02 after the decimal points making three digits in total, so insert the decimal point into the answer so that there are three digits after it: 50 → 0.050

⇒ 2.5 x 0.02 = 0.05