It has to be a number X such that X-1 is divisible by 4, an even number of times.
How about 25?
How about 25?
We know that there is an even number in each group, and there is one left over. This means the number must be odd.
Given that you are a number between 20 and 30, we can narrow down the possibilities to 21, 23, 25, 27, and 29.
Now let's divide each of these numbers into 6 equal groups and see if there is one left over:
- For number 21, if we divide it into 6 equal groups, we get 3 members in each group and 3 left over. So, 21 is not the answer.
- For number 23, if we divide it into 6 equal groups, we get 3 members in each group and 5 left over. So, 23 is not the answer.
- For number 25, if we divide it into 6 equal groups, we get 4 members in each group and 1 left over. So, 25 is the answer!
Thus, if you are a number between 20 and 30 and there is an even number in each of the 6 groups with 1 left over, you must be the number 25.