Hey You!
When you estimate multiplying 3.9 × 5.3 it helps you find the decimal point because you know that it should be close to the number. Like, rounding 3.9 to 4 and 5.3 to 5 and then multiplying it will give you 20, Now that you have your estimate, you know that the decimal point must be after the 20 because it's closer to the real number.
