One - the four. None of the trailing 0s are significant digits.
One - the trailing zeros are not significant.
1
4000000
One. The zeros are just placeholders.
Just the one and it is 4
One - the zeros are placeholders unless indicated.
1 significant figure. It can also be written as 4x10^6 (one sig fig)
1 significant figure.
1 significant figure.
One significant figure.
Five. All nonzero digits are significant and zeros in between significant digits are significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.