What is 125 rounded to the nearest ten?

Answer 1

120

Answer 2

10

Answer 3

120.

There are very good statistical reasons why 5 should be rounded to an even digit, and these are given below. If you just want the answer, skip all that follows.

Ignoring 5, for a moment:

You do not round 0.

You round 1,2,3 and 4 down

You round 6,7,8 and 9 up

This is balanced. Any number is equally likely to end in one of the digits 0-9 and, still leaving out 5, statistically speaking you would expect to round up half the time and round down half the time.

Now, if you round 5 up every time, you introduce an upward bias in your rounded numbers. There is a greater likelihood that the sum of the rounded numbers will be larger than the sum of the originals. Conversely, if you round 5s down every time you introduce a downward bias.

There are two possible solutions: one is to round up and down alternately or randomly. The problem with that is someone trying to follow your work might not be able to replicate your results. So, instead, you use the other option and round the number so that the final significant digit is even.

Answer 4

13

Answer 5

135

Answer 6

12