multiplications with 0’s in the end of the factors and products

Look at the following equations:

1. 70 x 4=280

2. 70 x 40=2,800

3. 700 x 4=2,800

4. 700 x 40=28,000

5. 7,000 x 40=280,000

What can we learn from the above equations?

All the equations have four numbers in common: 7 , 4 , their products, 28 and 0’s.

Here is the trick: when you try to get the answer of 7,000 x 40, you only need to take two steps:

First: Find the product of 7 and 4, which is 28;

Secondly: count the number of 0’s in both 7,000 and 40, which is 4; put the four 0’s after 28.

Therefore, the product of 7,000 and 40 is 280,000

The last thing that you want to do is to multiply 0’s by 0’s in the numbers.