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How can you tell whether a number is divisible by another number (leaving no remainder) without actually doing the division?

[ maths ]
asked on 21 Jan 2011
Abigail Silva Abigail Silva
14 Q, 0 A, 0 C
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Best Answer
1
2: If the last digit is even, the number is divisible by 2.
3 : If the sum of the digits is divisible by 3, the number is also divisible by 3.
4 : If the last two digits form a number divisible by 4, the number is also divisible by 4.
5 : If the last digit is a 5 or a 0, the number is divisible by 5.
6 : If the number is divisible by both 3 and 2, it is also divisible by 6.
7 : Take the last digit, double it, and subtract it from the rest of the number; if the answer is divisible by 7 (including 0), then the number is also.
8 : If the last three digits form a number divisible by 8, then so is the whole number.
9 : If the sum of the digits is divisible by 9, the number is also.
10 : If the number ends in 0, it is divisible by 10.
11 : Alternately add and subtract the digits from left to right. If the result (including 0) is divisible by 11, the number is also. Example: to see whether 365167484 is divisible by 11, start by subtracting: 3-6+5-1+6-7+4-8+4 = 0; therefore 365167484 is divisible by 11.
12 : If the number is divisible by both 3 and 4, it is also divisible by 12.
13 : Delete the last digit from the number, then subtract 9 times the deleted digit from the remaining number. If what is left is divisible by 13, then so is the original number.
answered on 21 Jan 2011
Joe Seb Joe Seb
0 Q, 23 A, 0 C
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