without multiplying, how do you know that the product of 399 and 48 is smaller than 20,722?

Answer 1

what is 50x400?

Answer 2

20,000

Answer 3

Since 399 is less than 400 and 48 is less than 50, then obviously the answer must be less than 20,000. Right?

Answer 4

the world in the 1400s

Answer 5

how can you show without multiplying that 4/9 is greater then 0.4