Handling multiplication and division of decimals follows specific steps to ensure accuracy. Let’s break it down with examples and explanations:

1. Multiplication of Decimals

Steps:

1. Ignore the decimal points initially and multiply the numbers as if they were whole numbers.
2. Count the total number of decimal places in both the numbers being multiplied.
3. Place the decimal point in the product, ensuring it has the same number of decimal places as the total you counted in Step 2.

Example:

For 0.001 × 7.23 (Question 17):

1. Multiply $1 \times 723 = 723$ (ignore decimals for now).
2. Count decimal places:
   • 0.001 has 3 decimal places.
   • 7.23 has 2 decimal places.
   • Total decimal places = $3 + 2 = 5$.
3. Insert the decimal point so the product has 5 decimal places:
   • Result = 0.00723.

2. Division of Decimals

Steps:

1. If the divisor (the number you're dividing by) is not a whole number, move the decimal point to the right to make it a whole number. Move the decimal point in the dividend (the number being divided) by the same number of places.
2. Perform the division as you would with whole numbers.
3. Place the decimal point in the quotient (result) directly above where it appears in the dividend.

Example:

For 0.00027 ÷ 9 (Question 19):

1. The divisor (9) is already a whole number. No adjustment needed.
2. Perform the division:
   • $0.00027 \div 9 = 0.00003$.
3. Result = 0.00003.

For 1.8 ÷ 0.06 (Question 20):

1. Move the decimal in the divisor (0.06) two places to the right to make it 6.
   • Move the decimal in the dividend (1.8) two places as well, making it 180.
2. Perform the division:
   • $180 \div 6 = 30$.
3. Result = 30.

How to Apply These Methods to Your Questions:

Here are the solutions to each problem in the table:

1. 16: $0.3 + 0.7 + 0.6 = 1.6$
   Result: $\textbf{1.6}$.

2. 17: $0.001 \times 7.23 = 0.00723$
   Result: $\textbf{0.00723}$.

3. 18: $4.3 \times 2 \times 0.003 = 0.0258$

   • $4.3 \times 2 = 8.6$, $8.6 \times 0.003 = 0.0258$. Result: $\textbf{0.0258}$.

4. 19: $0.00027 \div 9 = 0.00003$
   Result: $\textbf{0.00003}$.

5. 20: $1.8 \div 0.06 = 30$
   Result: $\textbf{30}$.

Would you like detailed steps for any specific problem?

Here are 5 relative questions to expand your understanding:

1. How do you handle subtraction or addition of decimals with varying decimal places?
2. What is the best way to check your answer when multiplying decimals?
3. Can you explain how to simplify calculations when dividing by small decimals (like 0.001)?
4. How do you interpret decimal results in real-world applications like money or measurements?
5. How does rounding decimals affect multiplication and division results?

Tip: Always align decimal points vertically when adding or subtracting decimals to avoid mistakes!