it is enough to look for the last two digits for divisibility for what no. a:20 b:12 c:56 d :123
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a)20 as if a number adds with 2 even numbers with last digit 0
meera21:
correct
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Numerals whose alternating sum of digits is divisible by 11 represent numbers divisible by 11:
Numerals whose sum of digits is divisible by 9 represent numbers divisible by 9:
for 7
Mark off the digits in groups of threes, just as you do when you put commas in large numbers. Starting from the right, compute the alternating sum of the groups as three-digit numbers. If the result is negative, ignore the sign. If the result is greater than 1000, do the same thing to the resulting number until you have a result between 0 and 1000 inclusive. That 3-digit number is divisible by 7 if and only if the original number is too
Numerals whose sum of digits is divisible by 9 represent numbers divisible by 9:
for 7
Mark off the digits in groups of threes, just as you do when you put commas in large numbers. Starting from the right, compute the alternating sum of the groups as three-digit numbers. If the result is negative, ignore the sign. If the result is greater than 1000, do the same thing to the resulting number until you have a result between 0 and 1000 inclusive. That 3-digit number is divisible by 7 if and only if the original number is too
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