
Arundeep

DIVISIBILITY BY SEVEN : First of all we recall the osculator for 7. Once again, for your convenience, as 7 x 3 =21 (one more than 2 x 10), our negative osculator is 2. This oscuator '2' is our keydigit. This and only this digit is used to check the divisibility of any number by 7. See how it works :Ex 1 : Is 112 divisible by 7 ? Soln: Step I : 11 2 : 11  2 x 2 = 7 As 7 is divisible by 7, the number 112 is also divisible by 7. Ex 2 : Is 2961 divisible by 7 ? Soln: Step I : 296 1: 296  1 x 2 = 294 Step II: 29 4 : 29 4  4 x 2 = 21 As 21 is divisible by 7, the number is also divisible by 7. Ex 3 : 5527783 8: 5527783  8 x 2 = 5527767 552776 7 : 552776  7 x 2 = 552762 55276 2 : 55276  2 x 2 = 55272: 5527 2: 5527  2 x 2 = 5523 552 3 : 552  3 x 2 = 546 54 6 : 54  6 x 2 = 42 As 42 is divisible by 7, the number is also divisible by 7. Note : 1. In all the examples each of the numbers obtained after the equal sign (=) is also divisible by 7. Whenever you find a number which looks divisible by 7, you may stop there and conclude the result without any hesitation. 2. The above calculations can be done in one line or even mentally. Try to do so. 