Verified Answer :

olemakpadu

3.9 5.3 ≈  4 5

≈20

Well after doing your multiplication, you can place your decimal point by knowing that from estimation the answer is around 20.

So you can place your decimal point after the first two digits from the left. 

Estimations are like rounding

Steps to solve 

1. turn 3.9 to 4

2. Turn 5.3 to 5

3. Multiply 4*5

4. you're answer should be 20
 
5. Now put the decimal to the left of 20

Explanation:

Estimating helps you because it makes it easier for you to multiply after you round.