40 correct to 3 significant figure
To round 40 to 3 significant figures, we need to consider the first three most significant digits, counting from the left.
In this case, we have the digits 4, 0, and 0. Since 4 is greater than 5, we need to round up the last significant digit. Therefore, the number 40, rounded to 3 significant figures, would be 40.0.
Note that if the last significant digit were less than 5, we would not have to round up, and the number would remain unchanged.