Page 81 - Math Smart - 7

4.21 Adding and subtracting decimals recall

When you add and subtract decimals, make sure that the decimal points are lined
O Find the sum.
up. You can use a place-value table to help you align the digits in the correct
1.08
place-value columns. Then add and subtract as normal but remember to write the
+ 0.85
decimal point in the answer.
O Find the difference.
4.12
-1.68
David goes for walks in a park every Sunday. He walks 2.62 km in the
morning and 1.3 km in the afternoon. How many kilometres does David walk
altogether every Sunday?
2.62 + 1.3 = ?
-ft
1
Write the numbers in a Fill in zeros in the empty Add or subtract
place-value table. Make spaces in the place- using column
sure that each digit is in value table so that the addition or
the correct place-value decimals you are adding subtraction.
column and that the or subtracting have the
decimal points are in line. same number of digits.

U . t h U . t h U . t h
2 .62 2 . 62 2 . 62
+ 1 .3 + 1 . 3 0—write zero + 1 . 30
9 2
t
line up the decimal points David walks 3.92 km
altogether every Sunday.

O Bo signed up for 3.3 gigabytes of mobile data. She has used 2.62 gigabytes.
How many gigabytes of data did she have left?
Regroup 3 units into 2 units 10
tenths. Add the tenths.
10 tenths + 2 tenths = 12 tenths
Regroup 3 tenths into 2 tenths
1
f and 10 hundredths.
U . t h U . t h U . t h
3 . 3 0-«—write zero 1^°
3 . 3
-2 . 62 +2 . 62 +2 . 6 2
0 . 68
t
line up the decimal points Bo had 0.68 gigabytes
of data left.