Chapter 1
Lesson 1-13
Page 40
Key Idea
You can use place
value to subtract
decimals.
Subtracting Decimals
How can you subtract decimals?
Heather caught a trout weighing 3.5 pounds
and a bass weighing 1.32 pounds. How much
more does the trout weigh than the bass?
Subtract 3.5 – 1.32.
Estimate: 3 – 1 = 2. Since 0.5 > 0.32 the difference
should be more than 2.
What You
Think
What You
Write
Write the
numbers,
lining up
the decimal
points.
Write zeros to
show place
value.
Subtract the
hundredths.
Decide if
you need to
regroup.
Regroup 5 tenths as 4 tenths and
10 hundredths.
Subtract the tenths and the ones. Decide if you need to regroup. Place the decimal point in the answer.
The difference 2.18 is more
than 2, so it is reasonable.
Check: 2.18 + 1.32 = 3.50
The answer checks.
The trout weighs 2.18 pounds more than the bass.
Talk About It
1.
Explain why 5 tenths equal 4 tenths and 10 hundredths.
2.
Why can you add to check subtraction?