Adding and Subtracting Meters and Centimeters 3B: 6.1c

Adding m & cm with no renaming 2 m 60 cm + 25 cm = _____ m _____ cm How do you get the answer? Since there are no meters in front of 25

cm, just add the centimeters.

852

Adding m & cm with renaming 2 m 60 cm + 75 cm = _____ m _____ cm You can still add the centimeters since

there are no meters in front of the 75 cm.

60 cm + 75 cm = 135 cm Can you leave the 135 cm as it is? Convert it into m and cm. 1 m 35 cm2 m 60

cm2 m 135 cm =

3 m 35 cm

+ 75 cm

3 35

Another way You could also make 100 with either 60

cm or 75 cm.

35 cm 25 cm

2 m 60 cm

75 cm

1 m

+

2 m 35 cm +

= 3 m 35 cm

Another way Now let’s make 100 with the 60. How

much do we need from the 75? How much is left?

35 cm40 cm

2 m 60 cm

75 cm

1 m

+

2 m +

= 3 m 35 cm35 cm

One more strategy… You can add the numbers up vertically. First, convert into cm. Add. Convert back to m and cm.

2m 60 cm+ 75 cm

260 cm+ 75 cm 335 cm3m 35 cm

Adding both meters and centimeters 2 m 65 cm + 3 m 20 cm = _____ m

_____cm Use mental calculation to add the

meters. Then add the centimeters.2 m 65 cm + 3 m 20

cm5 m 65 cm + 20 cm

5 m 85 cm

Adding both meters and centimeters Try this one… 2 m 65 cm + 3 m 40 cm = _____ m

_____cm Add the meters. Then add the centimeters and rename.2 m 65 cm + 3 m 40

cm5 m 65 cm + 40 cm

5 m 105 cm6 m 5 cm

Use vertical adding, if you prefer First, convert into cm. Add. Convert back to m and cm.

2 m 65 cm+3 m 40

cm

265 cm+ 340 cm 605 cm6 m 5

cm

Subtracting both meters and centimeters 5 m 30 cm – 25 cm = _____m _____ cm To find the answer, subtract 25 cm from

30 cm. There are no meters to take away so the 5 m stays the same.

5 5

Subtracting both meters and centimeters 5 m 30 cm – 75 cm = _____m _____ cm Take 100 cm from the 5 meters. What’s

left? Subtract the 75 from the 100. Add the remaining cm together.

4 55

5 m 30 cm

4 m 30 cm 100 cm

75 cm =–

75 cm– = 4 m 30 cm + 25 cm

= 4 m 55 cm

Other strategies Is there another way to solve the

problem 5 m 30 cm – 75 cm? You can rename 5 m 30 cm. Then subtract.

5 m 30 cm – 75 cm =

4 m 130 cm – 75 cm =4 m 55 cm

Use vertical subtracting, if you prefer First, convert into cm. Subtract. Convert back to m and cm.

5 m 30 cm– 75

cm

530 cm– 75 cm

455 cm4 m 55 cm

Subtracting when you don’t have to rename 5 m 30 cm – 2 m 25 cm = ____ m _____

cm How should we solve this? Subtract meters first. Then subtract centimeters.

5 m 30 cm

3 m 30 cm

3 m 5 cm– 2 m – 25 cm

How do we find the difference between 5 m 30 cm and 2 m 75 cm?

Let’s look at three subtraction strategies…

5 m 30 cm – 2 m 75 cm =

3 m 30 cm – 75 cm =

2 m 130 cm – 75 cm =

5 m 30 cm

2 m 30 cm 100 cm

2 m 75 cm =–

75 cm– = 2 m 30 cm + 25 cm

= 2 m 55 cm

2 m 55 cm

3 m 30 cm 75 cm =–

5 m 30 cm– 2 m 75 cm

530 cm– 275 cm

255 cm2 m 55 cm

RENAME CONVERT

MAKE 100

Now you try. Textbook page 12 Tasks 14-15 14 a) 5m 25cm b) 1m 55cm 15 a) 9m 32cm b) 3m 79cm c) 8m 30cmd) 6m 46cm e) 3m 20cm f) 9m 1cm g) 6m 15cm h) 5m 24cm i) 4m 55cm j) 3m 95cm k) 3m 55cm l) 2m 30cm

Extra practice and/or Homework WB pages 9-10 EP 113-114 Review 1B