# [RUBY] Find the difference from a multiple of 10

What I've been working on right now It was to enter a positive integer and output True if it was less than or equal to a multiple of 10 and False otherwise.

``````def near_ten(num)
basis = (num + 5) / 10 * 10
difference = (num - basis).abs
if difference <= 2
puts "True"
else
puts "False"
end
end
``````

First, let `basis` be the multiple of 10 that is closest to` num`.

The second line calculates the numbers suitable for `basis`.

``````  basis = (num + 5) / 10 * 10
``````

As an example, if it is an integer from 15 to 24, the nearest multiple of 10 is 20, so I want to use 20 as a reference. Add 5 to each of these integers to get 20-29. These integers have 2 in the tens place, so if you do `/ 10 * 10` respectively, 20 will come out, which is the number you want to use as a reference.

Other integers work just as well.

This completes the `basis` part.

Next, the difference between the original number and this standard is calculated.

``````num - basis
``````

Since the difference may be negative as it is, we use a method that gives an absolute value.

``````(num - basis).abs
``````

Then substitute this

``````difference = (num - basis).abs
``````

If the difference `difference` obtained in this way is 2 or less, it is sufficient, so it is judged and the process ends.

``````  if difference <= 2
puts "True"
else
puts "False"
end
``````