We can subtract numbers that include decimals in just the same way as we would subtract whole numbers. We just need to line up the numbers according to their place value.
Evaluate: $21.952-5.719$21.952−5.719
Think: How do the place value columns line up?
Do: $21.952-5.719=16.233$21.952−5.719=16.233
We can also use this for questions that involve money, distances or any number that involves decimals.
Evaluate: $\$18.52-\$1.28$$18.52−$1.28
Think: Line up the place value columns
Do: $\$18.52-\$1.28=\$17.24$$18.52−$1.28=$17.24
Remember the names from the columns on the place value table- tenths, hundredths, thousandths and so on. When we convert decimals to fractions, these names tell us what the denominator (the bottom number) of our fractions will be.
Think: A mixed number is an answer with a whole number and a fraction
Do:
$7.45-3.7$7.45−3.7 | $=$= | $3.75$3.75 |
$=$= | $3\frac{75}{100}$375100 | |
$=$= | $3\frac{3}{4}$334 |
Now let's use this to solve some questions!
Evaluate: Evaluate $0.94-0.3$0.94−0.3, giving your answer as a simplified fraction
Think: To simplify a fraction, we need to find common factors between the numerator and the denominator
Do:
$0.94-0.3$0.94−0.3 | $=$= | $0.64$0.64 | |
$=$= | $\frac{64}{100}$64100 | ($4$4 is a common factor) | |
$=$= | $\frac{16}{25}$1625 |
Evaluate $9.9-5.5$9.9−5.5
$9$9 | $.$. | $9$9 | |
$-$− | $5$5 | $.$. | $5$5 |
$\editable{}$ | $.$. | $\editable{}$ |
Find $3-0.8$3−0.8, leaving your answer in decimal form.
Evaluate $8.2-2.13-4.938$8.2−2.13−4.938