Question

multiply the decimal numbers together. choose the correct answer.

1. 0.8·0.9

(a) 0.72
(b) 0.072
(c) 7.2

1. 0.02·0.25

(a) 0.50
(b) 0.0050
(c) 0.050

1. 0.75·0.2

(a) 0.15
(b) 0.015
(c) 1.50

1. 0.5·4.8

(a) 0.024
(b) 0.24
(c) 2.40
activity 2
multiply using the traditional method. check your work using rounding.

1. 0.75·0.8
2. 0.029·0.1
3. 0.54·0.7
4. 0.25·0.4
5. 0.1·0.08
6. 2.5·0.5

activity 3
circle the graphs that show indirect relationships.
graph a
graph b
graph c
graph d

Explanation:

Activity 1

Question 1

Step1: Multiply numbers ignoring decimals

$8\times9 = 72$

Step2: Count decimal places

$0.8$ has 1 decimal - place and $0.9$ has 1 decimal - place, so total 2 decimal places.
$0.8\times0.9=0.72$ (a)

Question 2

Step1: Multiply numbers ignoring decimals

$2\times25 = 50$

Step2: Count decimal places

$0.02$ has 2 decimal - places and $0.25$ has 2 decimal - places, so total 4 decimal places.
$0.02\times0.25 = 0.0050$ (b)

Question 3

Step1: Multiply numbers ignoring decimals

$75\times2=150$

Step2: Count decimal places

$0.75$ has 2 decimal - places and $0.2$ has 1 decimal - place, so total 3 decimal places.
$0.75\times0.2 = 0.15$ (a)

Question 4

Step1: Multiply numbers ignoring decimals

$5\times48 = 240$

Step2: Count decimal places

$0.5$ has 1 decimal - place and $4.8$ has 1 decimal - place, so total 2 decimal places.
$0.5\times4.8 = 2.40$ (c)

Activity 2

Question 1

Step1: Multiply as whole numbers

$75\times8 = 600$

Step2: Count decimal places

$0.75$ has 2 decimal - places and $0.8$ has 1 decimal - place, so total 3 decimal places.
$0.75\times0.8=0.600 = 0.6$
Rounding: $0.75\approx0.8$ and $0.8$ remains $0.8$, $0.8\times0.8 = 0.64\approx0.6$

Question 2

Step1: Multiply as whole numbers

$29\times1 = 29$

Step2: Count decimal places

$0.029$ has 3 decimal - places and $0.01$ has 2 decimal - places, so total 5 decimal places.
$0.029\times0.01=0.00029$
Rounding: $0.029\approx0.03$ and $0.01$ remains $0.01$, $0.03\times0.01 = 0.0003\approx0.00029$

Question 3

Step1: Multiply as whole numbers

$54\times7 = 378$

Step2: Count decimal places

$0.54$ has 2 decimal - places and $0.7$ has 1 decimal - place, so total 3 decimal places.
$0.54\times0.7 = 0.378$
Rounding: $0.54\approx0.5$ and $0.7$ remains $0.7$, $0.5\times0.7 = 0.35\approx0.378$

Question 4

Step1: Multiply as whole numbers

$25\times4 = 100$

Step2: Count decimal places

$0.25$ has 2 decimal - places and $0.4$ has 1 decimal - place, so total 3 decimal places.
$0.25\times0.4 = 0.100 = 0.1$
Rounding: $0.25\approx0.3$ and $0.4$ remains $0.4$, $0.3\times0.4 = 0.12\approx0.1$

Question 5

Step1: Multiply as whole numbers

$1\times8 = 8$

Step2: Count decimal places

$0.1$ has 1 decimal - place and $0.08$ has 2 decimal - places, so total 3 decimal places.
$0.1\times0.08 = 0.008$
Rounding: $0.1$ remains $0.1$ and $0.08\approx0.1$, $0.1\times0.1 = 0.01\approx0.008$

Question 6

Step1: Multiply as whole numbers

$25\times5 = 125$

Step2: Count decimal places

$2.5$ has 1 decimal - place and $0.5$ has 1 decimal - place, so total 2 decimal places.
$2.5\times0.5 = 1.25$
Rounding: $2.5$ remains $2.5$ and $0.5$ remains $0.5$, $2.5\times0.5 = 1.25$

Answer:

Activity 1

1. a. 0.72
2. b. 0.0050
3. a. 0.15
4. c. 2.40

Activity 2

1. $0.75\times0.8 = 0.6$
2. $0.029\times0.01 = 0.00029$
3. $0.54\times0.7 = 0.378$
4. $0.25\times0.4 = 0.1$
5. $0.1\times0.08 = 0.008$
6. $2.5\times0.5 = 1.25$