Multiply 3.6 by 0.4. What is the product?

• A. 1.44
• B. 1.6
• C. 0.144
• D. 14.4

Answer: (A)

When multiplying decimals, multiply as if they are whole numbers and then place the decimal point based on the total number of decimal places in both factors. Here, 3.6 has one decimal place and 0.4 has one decimal place, so the product should have two decimal places.

Compute 36 × 4 = 144, then place the decimal two digits from the right to get 1.44. This is the exact product.

If you round first, you might get 1.6, which is an over-simplification. If the decimal point is placed incorrectly, you could get 0.144 or 14.4, which come from misplacing the decimal or treating 0.4 as 0.04 or 4, respectively.