Divisibility Rules 1 to 20

Music:
"Secrets of the Schoolyard" by Kevin MacLeod

[YenjiJem]

Video was suggested by RaGHAFazKa MuHaMMaD

[brocraftandknowledge]

Divisiblity of 17-
-multiply the last number with 5
-then subtract with remaining number
-if the result is multiple of 17 and it may also negative or positive and 0
For ex- 204, 4×5=20, 20-20=0.zero
187, 7×5=35, 18-35=-17.negative
765, 5×5=25, 76-25=51.positive

[daffa_fm]

21: follow rules for 7 and 3
22: follow rules for 2 and 11
24: follow rules for 8 and 3
26: follow rules for 2 and 13
28: follow rules for 4 and 7
30: follow rules for 3 and 10 or 2 and 15
33: follow rules for 3 and 11

[JkC]

Much better than what my school taught.

[YYHoe]

Alternative rules for 4, 8 and 16:
4: If after division by 2, the number is still even, the number is divisible by 4.
8: If after division by 2 twice, the number is still even, the number is divisible by 8.
16: If after division by 2 thrice, the number is still even, the number is divisible by 16.

[marcusscience]

Rather than list out all the numbers one by one, here are generalised rules, the positive integers split into 4 categories:

Powers of 2 (2^n): check last n digits
Powers of 5 (5^n): same as above
Relatively prime with 10 (p): multiply last digit by 10^[-1] mod p (modular multiplicative inverse) and add remaining truncated digits
(repeat as necessary)
Other composites: apply rules of greatest factors belonging in each of the above categories (if present)

[felicity]

Why does the 17 divisibility rule stating that it should be added, but in the example it was subtracted? Which should be done? Add or subtract?

[simrangupta]

short and crisp. loved it and thank you for making such a wonderful video

[sourajitboral]

Precise. Very helpful. Though there's a mistake in 17 divisibility rule, apart from that it's very time saving. Appreciate your hard work.

[abdullafahar]

Amazing video. How fast, effective, and cool edits to make us understand. You really deserve much more for this video. Thank you

[ÞeOfficialCeresouslyAnimatesYT]

2:22 if you apply that rule for 17, then the result would be 34, and if you apply that rule for 34, then the result would be 17

[LaGGSBD]

For divisibilty rule of 7, you can also take out the last digit, multiply the remaining by 3 and then add the digit you removed to the result.

[emmazepeda]

Rules from 101-200 (not completed)
101: take the last digit, multiply it by 10 and subtract it from the remaining digits
102: apply rules of 51 and 2
103: take the last digit, multiply it by 31 and add it to the remaining digits
104: apply rules of 13 and 8
105: apply rules of 21 and 5
106: apply rules of 53 and 2
107:
108:
109: take the last digit, multiply it by 11 and add it to the remaining digits
110: apply rules of 10 and 11
111: take the last digit, multiply it by 11 and subtract it from the remaining digits
112:
113:
114:
115:
116:
117:
118:
119:
120: apply rules of 10 and 12
121: take the last digit, multiply it by 12 and subtract it from the remaining digits
122: take the last digit, multiply it by 6 and subtract it from the remaining digits
123:
124:
125: last three digits must be a multiple of 125 (125, 250, 375, 500, 625, 750, 875 and 000)
126:
127:
128: last seven digits must be a multiple of 128
129:
130: apply rules of 10 and 13
131:
132: apply rules of 66 and 2
133:
134:
135:
136:
137:
138: apply rules of 23 and 6
139:
140: apply rules of 10 and 14
141:
142: apply rules of 71 and 2
143:
144: apply rules of 48 and 3
145:
146:
147:
148:
149:
150: apply rules of 10 and 15
151:
152:
153:
154: apply rules of 77 and 2
155:
159:
160: apply rules of 10 and 16
161:
162:
163:
164: apply rules of 82 and 2
165:
166:
167:
168:
169:
170: apply rules of 10 and 17
171:
172: apply rules of 86 and 2
173:
174:
175:
176:
177:
178:
179:
180: apply rules of 10 and 18
181: take the last digit, multiply it by 18 then subtract it from the remaining digits
182:
183:
184:
185: apply rules of 37 and 5
186:
187:
188:
189:
190: apply rules of 10 and 19
191: take the last digit, multiply it by 19 and subtract it from the remaining digits
192:
193:
194:
195:
196: apply rules of 98 and 2
197:
198: apply rules of 33 and 6
199:
200: last three digits must be 200, 400, 600, 800 and 000

BONUS: 0.5: last decimal digit must be .0 or .5

[kanchanmishra]

Who else expected divisibility of 20 to be like " apply 4 &5 "

[Henrique.tRo_Real]

50: Last digits must be 50 or 00.
60: Apply rules for 3 and 20.
101: Multiply the last dight by 10 and subtract it from the remaining digits
103: Multiply the last digit by 31 and add it to the remaining digits.
104: Apply rules for 13 and 8.
105: Apply rules for 21 and 5
106: Apply rules for 53 and 2.
125: Last three digits must be 125, 250, 375, 500, 625, 750, 875 or 000.
151: Multiply the last digit by 15 and subtract it from the remaining digits.

[tomgraham]

Trouble spelling the word "multiply" for segments covering 13, 17, and 19. And the "add" wording for the 17 segment should say, "subtract." Otherwise, a stunning video we love!

[YYHoe]

For 4, 8 and 16, if ur lazy and don't wanna do long division, just see if can divide by 2 twice, thrice and four times respectively. Works.

[sevturner]

0:46 or you can multiply 1's digit by 5 then add that to the remaining example: 123 is 12+(3x5)

[hetalbrahmbhatt]

Thanks bro, it helped me in my project!!

[darkskywithmoon]

Thanks for your help wish you all good healthy