Multiply a Whole Number by a Decimal to the Hundredths Place
Multiply a Whole Number by a Decimal to the Hundredths Place is a Grade 5 math skill from Eureka Math that teaches students to multiply whole numbers by two-decimal-place decimals. Students apply the standard multiplication algorithm treating the decimal as a whole number, then place the decimal point in the product based on the total number of decimal places (two for hundredths). This skill builds decimal multiplication fluency.
Key Concepts
To multiply a whole number by a decimal with hundredths, first multiply the numbers as if they were both whole numbers. Because the decimal factor is 100 times smaller than its whole number form (e.g., $0.25$ is 100 times smaller than $25$), the product must be adjusted by dividing by 100. This is equivalent to placing the decimal point two places from the right in the final product.
Common Questions
How do you multiply a whole number by a decimal to the hundredths place?
Ignore the decimal point and multiply as whole numbers. Then count the decimal places in both factors (two for a hundredths decimal) and place the decimal point that many places from the right in the product.
What is 7 x 0.45?
Multiply 7 x 45 = 315. The factor 0.45 has 2 decimal places, so place the decimal 2 places from the right: 3.15. So 7 x 0.45 = 3.15.
Why does the product of a whole number and a hundredths decimal have two decimal places?
The decimal has denominator 100. Multiplying by a whole number does not add more decimal places, so the product inherits the two decimal places from the 0.xx factor.
What Eureka Math Grade 5 chapter covers multiplying whole numbers by hundredths?
Eureka Math Grade 5 covers multiplying whole numbers by hundredths decimals in its decimal multiplication chapters as part of the standard algorithm curriculum.
How can you check a decimal multiplication answer using estimation?
Round 0.45 to 0.5 and multiply: 7 x 0.5 = 3.5. Your answer of 3.15 is close to 3.5, so it is reasonable.