Round 691 to 1 significant figure!

The correct answer is: 700

Explanation:

To round to one significant figure, identify the first nonzero digit and consider the digit that follows it (leading zeros are not counted; an example follows below).

In 691 the leading digit (the hundreds place) is 6. Look at the next digit, 9; because 9 is greater than 5, the 6 rounds up to 7 and the remaining digits become zeros, giving 700.

(EXTRA INFORMATION) Zero case:

For a number like 0.951 the initial zero is not significant, so the first significant digit is 9 after the decimal. The next digit is 5, so 0.951 rounds to 1.0 when rounded to one significant figure.