Divisibility
Kisi 2 digit k number ki divisiblity check krna ho to ...
Ek hi prime k kayi divisibility ho Sakti hn .
For 11
11 = 1 + a
(A + 10B)
121 = 12+10 = 22 ✅
For 13
13a = 1 ± 3k jo kaam idhar karenge wo , SB jgh valid Hoga.
13 = 1 + 3*4 so , (p + 4k) divisiblity check Kar sakte ho.
Mtlb (last k digit Ka 4 times + first digits ) multiple of 13 Hona Chahiye .
For Ex
52 = 5 + 2*4 = 13 ✅
65 = 6 + 5*4 = 26 ✅
273 = 27 + 3*4 = 39 ✅ aise.
For 17
17a = 1 ± 7k
17*2 = 1 - 7*5 (p-5k) bn gya
For Ex
85 = 8 - 5*5 = -17 ✅
901 = 90 - 1*5 = 85 ✅ aise.
For 19
19a = 1 + 9k
19*1 = 1 + 9*2
So , (A+2B) divisiblity
1349 = 134 + 9*2 = 152 = 15 + 2*2 = 19 ✅
For 23
23a = 2 + 3k
23*1 = 2 + 3*7
(A + 7B)
115 = 11 + 5*7 = 46 ✅
1794 = 179 + 4*7 = 207 = 20 + 7*7 = 69 ✅
For 29
29a = 2 + 9b
(A + 3B)
1827 = 182 + 7*3 = 203 = 20 + 3*3 = 29 ✅
13804 = 1380 + 3*4 = 1392 = 139 + 6 = 145 = 14 + 5*3 = 29 ✅
Same follow......
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