So because 9 and 10 are close to each other, and the fact that 10 is really easy to multiply by, you do 473 x 10 which is 4730, because you just add a 0 to the end.
This means that an estimate is 4730 or if you want to be less specific, <4730, because 9 is less than 10.
The actual product though is 4257.