Divisible by 7 (Math Trick)...
A number is divisible by 7 if, subtract 2 times the last digit from the remaining number and its result is divisible by 7.
Let us we will apply this interesting math rule on following examples.
Is 203 divisible by 7?
Here the last number is 3 and remaining is 20. Apply the above rule. i.e. Double the last digit (3) and subtract it from remaining number (20)
Now the result 14 is divisible by 7 so 203 is divisible by 7.
(Do this step in your mind)
Is 3164 divisible by 7?
Here 308 is big number (If you feel difficult to divide you can apply the rule again).
Now the result 14 is divisible by 7 so the number 3164 is also divisible by 7.
(Do this step in your mind)
Is 108346 divisible by 7?
Now the result 91 is divisible by 7, so the number 108346 is also divisible by 7.
(Do this step in your mind)