Decimal Operations - Pre Algebra

1. What is $4.8 \div 0.6$?

   $8$. Multiply both by $10$ to get $48 \div 6$.

2. How do you place the decimal point when multiplying two decimals?

   Multiply as whole numbers, then give the product as many decimal places as the two factors have in total.

3. What is $1.5 \times 0.4$?

   $0.6$. Since $15 \times 4 = 60$, two decimal places give $0.60$.

4. What is $3.6 + 0.48$?

   $4.08$. Line up the points: $3.60 + 0.48$.

5. When adding or subtracting decimals in a column, what must be lined up?

   The decimal points, so that digits with the same place value line up. Zeros can fill empty places.

6. What is $2.5 \times 1.2$?

   $3$. Since $25 \times 12 = 300$, two decimal places give $3.00$.

7. What is $5 - 1.27$?

   $3.73$. Write $5$ as $5.00$, then subtract.

8. What is $0.045 \times 100$?

   $4.5$. Multiplying by $100$ moves the decimal point two places right.

9. What is $0.72 \div 0.08$?

   $9$. Multiply both by $100$ to get $72 \div 8$.

10. What is $0.3 \times 0.2$?

    $0.06$. Since $3 \times 2 = 6$ and the factors have two decimal places in total.

11. What is $3.5 \div 0.5$?

    $7$. Multiply both by $10$ to get $35 \div 5$.

12. What is the first step in dividing by a decimal such as $0.6$?

    Multiply the divisor and the dividend by the same power of $10$ so the divisor becomes a whole number. The quotient does not change.

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