Answer:
2,000
Explanation:
An easy way of solving problems like these is to count the number of zeros in the equation, temporarily remove them, solve the new problem, and then add all the zeros that you removed before. In this case:
100 x 20 = ?
1 x 2 = ? | 000
2 | 000
2,000
Here's another example:
300 x 5000 = ?
300 x 5000 = ?
3 x 5 = ? | 00000
15 | 00000
1,500,000