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Number Theory

Level 25 / mastery

Rules - digit-sum (3, 9)

3 visual steps / divisibility rule

1. Digit sum

divisible? 729 by 91. Digit sum7 + 2 + 9 = 18.17 + 2 + 9 = 18218 divisible by 93answer yes
7 + 2 + 9 = 18.

7 + 2 + 9 = 18.

2. Multiple of 9

divisible? 729 by 92. Multiple of 918 divisible by 9.17 + 2 + 9 = 18218 divisible by 93answer yes
18 divisible by 9.

18 divisible by 9.

3. Answer yes

divisible? 729 by 93. Answer yesanswer yes. Read answer answer yesanswer yes.
answer yes.

answer yes.

Practice Level 25

Use the visible move, then type only when the answer is clear.

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