If a number is divisible by three then sum must be a multiple of 3
for example; in case of number 123 then 1+2+3=6  here 6 is a multiple of 3 so it is divisible
if a number is divisible by 4 its last 2 digits are divisible by 4
for example 444 here last 2 digits are 44 it is divisible by 4 so the number is divisible
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When we add 3 digit no. and the sum of the 3 digits is the multiple of 3 then it is divisible by 3...
2+4+3=9, 9 is the multiple of 3 ..SO this no. is divisible by 3....

When the 3 digit no. is divisible by 2 ..then it is also divisible by 4
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