Decimal Rules
How do you add decimals?
You line up the decimals and then add the numbers.
31.9 + 46.5
78.4 - seventy-eight and four tenths
.6 x 2.1
1.26 - one and twenty-six hundredths
What is the greatest common factor (GCF) of 12 and 15?
3
3/10 x 2/3
6/30 and/or 1/5
How do you subtract decimals?
You line up the decimals and then subtract the numbers.
95.29 - 1.3
93.99 - ninety-three and ninety-nine hundredths
4.25 x 21
89.25 - eighty-nine and twenty-five hundredths
What is the least common multiple (LCM) of 4 and 9?
36
Change 5 2/5 into an improper fraction.
27/5
What are the next 3 place values to the right of the decimal?
Tenths, hundredths, and thousandths
5 + 2.78 + .030
7.81 - seven and eighty-one hundredths
11.2 x 0.31
3.472 - three and four hundred seventy-two thousandths
What is the greatest common factor (GCF) of 16 and 36?
4
Change 40/7 to a mixed number.
5 5/7
What do you do if there are not enough digits in the top number to subtract or add with decimals?
You have to add on zeros (place holders).
478.2 - 29.834
488.366 - four hundred eighty-eight and three hundred sixty-six thousandths
2.03 x .5
1.015 - one and fifteen thousandths
What is the least common multiple (LCM) of 20 and 12?
60
2 1/3 ÷ 1 1/4
1 13/15
How do you multiply decimals?
You multiply the numbers and then you count how many spaces there are to the right of the decimals and count them over to the left in the answer.
8.07 + 23.3 + 48
79.37 - seventy-nine and thirty-seven hundredths
25.7 x 3.2
82.24 - eighty-two and twenty-four hundredths
What is the least common multiple (LCM) of 21 and 24?
168
5 1/2 ÷ 4 1/8
1 1/3