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🔢 Quick Trick: Divisibility Rules 7, 11, 13

Check if 91 is divisible by 7 in seconds! Remove last digit, double it, subtract from remaining number.

Rajesh Kumar

Mathematics Expert

14 Jan 20262 min read1,100 views

Divisibility by 7

Remove last digit

Double it

Subtract from remaining

Repeat if needed

Example: 91

Remove 1, remaining = 9

Double 1 = 2

9 - 2 = 7 ✓ (divisible by 7)

Alternate sum difference

If result is 0 or divisible by 11, number is divisible

Example: 1331

(1+3) - (3+1) = 4 - 4 = 0 ✓

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