What Is the Divisibility Rule for 7?
The divisibility rule for 7 dictates that a number is divisible by 7 if subtracting 2 times the digit in the one's column from the rest of the number, now excluding the one's column digit, yields a number that is divisible by 7 or 0. Divisibility rules are simple rules that can be used to quickly determine if a number is divisible by a smaller number without a calculator.
To determine if the number 672 is divisible by 7, start by multiplying the last digit by 2, which in this case results in 4. Subtracting this from the rest of the number, 67 minus 4, yields 63. Since 63 can be divided by 7 evenly to result in 9, it is simple to conclude that 672 is divisible by 7.