Decimal Multiplication and Division Flashcards

Grade 5 · Math · Flashcards

Review key rules and practice problems for multiplying and dividing decimals.

Flashcards

Rule for multiplying decimals: Multiply as whole numbers, then place the decimal point so the product has the same total decimal places as both factors combined
1.2 x 3: 3.6; multiply 12 x 3 = 36, then place 1 decimal place
0.8 x 0.7: 0.56; multiply 8 x 7 = 56, then place 2 decimal places
Rule for dividing a decimal by a whole number: Place the decimal point in the quotient directly above the decimal point in the dividend, then divide normally
7.2 ÷ 9: 0.8; align the decimal, divide 72 ÷ 9 = 8, giving 0.8
Rule for dividing by a decimal: Multiply both dividend and divisor by a power of 10 to make the divisor a whole number, then divide
5.4 ÷ 0.6: 9; multiply both by 10 to get 54 ÷ 6 = 9
0.36 ÷ 0.04: 9; multiply both by 100 to get 36 ÷ 4 = 9
Estimating 4.8 x 2.1: About 10; round to 5 x 2 = 10 to check if your answer is reasonable
Place value: tenths, hundredths, thousandths: One place right of decimal = tenths (0.1); two places = hundredths (0.01); three places = thousandths (0.001)
Why does a product of two decimals less than 1 become smaller?: Multiplying by a number less than 1 is like taking a fraction of something, making it smaller
2.4 x 1.5: 3.60 = 3.6; multiply 24 x 15 = 360, then place 2 decimal places
15.5 ÷ 5: 3.1; align the decimal, divide 155 ÷ 5 = 31, giving 3.1