Question

do these problems in your head. use paper only for the problems that you just cant do in your head. its importan do as many of these problems without paper as you can.
do not use a calculator at all.
$4 \times 0.2 \quad = \quad \boxed{\quad}$
$0.02 \times 8 \quad = \quad \boxed{\quad}$
$0.5 \times 9 \quad = \quad \boxed{\quad}$
$50 \times 0.7 \quad = \quad \boxed{\quad}$
$40 \times 0.08 \quad = \quad \boxed{\quad}$
$0.4 \times 0.9 \quad = \quad \boxed{\quad}$
$0.5 \times 0.2 \quad = \quad \boxed{\quad}$
$700 \times 0.8 \quad = \quad \boxed{\quad}$
$9000 \times 0.9 = \quad \boxed{\quad}$
$0.03 \times 80 \quad = \quad \boxed{\quad}$

Explanation:

Step1: Convert decimal to fraction

$0.2 = \frac{2}{10}$, so $4 \times 0.2 = 4 \times \frac{2}{10} = \frac{8}{10} = 0.8$

Step2: Convert decimal to fraction

$0.02 = \frac{2}{100}$, so $0.02 \times 8 = \frac{2 \times 8}{100} = \frac{16}{100} = 0.16$

Step3: Convert decimal to fraction

$0.5 = \frac{1}{2}$, so $0.5 \times 9 = \frac{9}{2} = 4.5$

Step4: Convert decimal to fraction

$0.7 = \frac{7}{10}$, so $50 \times 0.7 = 50 \times \frac{7}{10} = 5 \times 7 = 35$

Step5: Convert decimal to fraction

$0.08 = \frac{8}{100}$, so $40 \times 0.08 = 40 \times \frac{8}{100} = \frac{320}{100} = 3.2$

Step6: Convert decimals to fractions

$0.4 = \frac{4}{10}$, $0.9 = \frac{9}{10}$, so $0.4 \times 0.9 = \frac{4 \times 9}{100} = \frac{36}{100} = 0.36$

Step7: Convert decimals to fractions

$0.5 = \frac{5}{10}$, $0.2 = \frac{2}{10}$, so $0.5 \times 0.2 = \frac{5 \times 2}{100} = \frac{10}{100} = 0.1$

Step8: Convert decimal to fraction

$0.8 = \frac{8}{10}$, so $700 \times 0.8 = 700 \times \frac{8}{10} = 70 \times 8 = 560$

Step9: Convert decimal to fraction

$0.9 = \frac{9}{10}$, so $9000 \times 0.9 = 9000 \times \frac{9}{10} = 900 \times 9 = 8100$

Step10: Convert decimal to fraction

$0.03 = \frac{3}{100}$, so $0.03 \times 80 = \frac{3 \times 80}{100} = \frac{240}{100} = 2.4$

Answer:

$4 \times 0.2 = 0.8$
$0.02 \times 8 = 0.16$
$0.5 \times 9 = 4.5$
$50 \times 0.7 = 35$
$40 \times 0.08 = 3.2$
$0.4 \times 0.9 = 0.36$
$0.5 \times 0.2 = 0.1$
$700 \times 0.8 = 560$
$9000 \times 0.9 = 8100$
$0.03 \times 80 = 2.4$