What is 1.2 × 4?

What is 1.2 × 4?

• A. 4.2
• B. 4.0
• C. 4.6
• D. 4.8

Answer: (D)

When multiplying a decimal by a whole number, multiply as if there were no decimals, then place the decimal point so the total number of decimal places matches the sum of decimal places in the factors. Here, 1.2 has one decimal place and 4 has none, so the product should have one decimal place. Multiply 12 by 4 to get 48, then place the decimal one place from the right to get 4.8. Another way to see it is 4 × 1.2 = 4 × 1 + 4 × 0.2 = 4 + 0.8 = 4.8. So the result is 4.8.

When multiplying a decimal by a whole number, multiply as if there were no decimals, then place the decimal point so the total number of decimal places matches the sum of decimal places in the factors. Here, 1.2 has one decimal place and 4 has none, so the product should have one decimal place. Multiply 12 by 4 to get 48, then place the decimal one place from the right to get 4.8. Another way to see it is 4 × 1.2 = 4 × 1 + 4 × 0.2 = 4 + 0.8 = 4.8. So the result is 4.8.