87985 is divisible by 7 or not ?

Combined test of divisibility for 7, 11 or 13.Method is useful for any big or small digit number.

Step 1 Make groups of 3 digits from the end (unit place) in above case groups are 87 985

Step 2 add all groups at odd places (1st, 3rd, 5th etc..) here only 1 group 985

Step 3 add all groups at even places (2nd, 4th, 6th, etc..) here only 1 group 87 (group may be of 1 or 2 or 3 digits depending on number of digits in given number)

Step 4 find difference in above 2 additions here 985 – 87 = 898

Step divide the difference by 7, 11, 0r 13 as the case may be.

898/7 = 128 2/7 it is not divisible 7, for test of eleven apply test not divisible by 11 and 898/13 = 69 1/3 not divisible by 13.

Even you can find remainder using this method.

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