Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The decimal system extends the place value system to represent parts of a whole using a decimal point. The places to the right of the decimal point are Tenths (), Hundredths (), and Thousandths ().
To compare two decimal numbers, first compare the whole number parts. If they are equal, compare the tenths digit. If those are also equal, compare the hundredths digit, and so on.
Decimals are used to convert units: , , and .
When multiplying a decimal by , the decimal point shifts to the right by as many places as there are zeros.
When dividing a decimal by , the decimal point shifts to the left by as many places as there are zeros.
To multiply two decimals, multiply them as if they were whole numbers. The number of decimal places in the product is the sum of the decimal places in the two factors.
To divide a decimal by another decimal, multiply both the dividend and the divisor by a power of (like ) to make the divisor a whole number, then divide.
📐Formulae
💡Examples
Problem 1:
Add and .
Solution:
Explanation:
Align the decimal points vertically and add column by column, carrying over just like whole number addition.
Problem 2:
Multiply by .
Solution:
Explanation:
First, multiply and as whole numbers: . The number of decimal places in is and in is . Total decimal places needed is . Placing the point gives .
Problem 3:
Divide by .
Solution:
Explanation:
To make the divisor a whole number, multiply both numerator and denominator by . This converts the problem to , which equals .