Answer: 3.2
Step-by-step explanation:
The left-most digits are more significant than digits on the right.
For example, in the very large number 1,234,567 the "1" and "2" are more important than the "6" and "7". We focus on the more important digits when rounding. This would mean 1,234,567 rounds to 1,200,000 = 1.2 million = 1.2*10^6
Going back to 3.162, we have "3" and "1" as the left-most digits. We'll bump 3.1 up to 3.2 because of the digit 6 fits the criteria of "5 or larger".
Put another way: 3.162 is closer to 3.2 than it is to 3.1
This is why 3.2 is the final answer.