Answer : The correct answer is 630.
Explanation :
The following rules are used to round off a number to the required number of significant figures:
(1) If the rightmost digit to be removed is more than 5, the preceding number is increased by one.
(2) If the rightmost digit to be removed is less than 5, the preceding number is not changed.
(3) If the rightmost digit to be removed is 5, then the preceding number is not changed if it is an even number but it is increased by one if it is an odd number.
As we are given, 634
In the given number, there are 3 significant figures. Now we have to convert it into 2 significant figures.
According to the rules, round off the given measurement in 2 significant figures as 630 because last number i.e 4 is less than number 5 so, last digit become 0.
Therefore, the correct answer is 630.