determine the location of the non significant zeros by rewriting the number and placing a bar over the zeroes that are not significant.
1. 8040
2. 4.2 x 10^5
3. 4.70 x 10^-6
We can't place bars over anything.
#2 has no zeros but I guess you could rewrite it as 42ssss and all of the zeros (represented by s) are non-significant zeros.
I would rewrite 1 as 8.04sE3 where s stands for the non-significant zero.
#3 can be written as 0.00000470 or s.sssss470. The trailing zero is the only significant one.