<span>To find the mean absolute deviation of the data, start by finding the mean of the data set.Find the sum of the data values, and divide the sum by the number of data values.Find the absolute value of the difference between each data value and the mean: ...<span>Find the sum of the absolute values of the differences.</span></span>
Yes; his answer is correct.
John can do this by multiple ways, but most likely he just remembered this one. Here are some ways.
1. He used his fingers; he put 1 finger, then another finger, and got 2 fingers up. The answer is 2.
2. He remembered it; usually Kindergarteners learn this and this is very easy to remember.
3. He used the things around him; I have 1 crayon then add another, how many do I have? 2.
.08
.21
.40
is the right answer