Question: Which of the following is a characteristic of numbers divisible by 7?

Options:

1. They end in 0 or 5
2. The double of the last digit subtracted from the rest of the number is divisible by 7
3. They are always even
4. They are always prime

Correct Answer: The double of the last digit subtracted from the rest of the number is divisible by 7

Solution:

A common rule for checking divisibility by 7 is to double the last digit and subtract it from the rest of the number; if the result is divisible by 7, then the original number is also divisible by 7.