How many two–digit numbers are divisible by 3? – InterviewSolution

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1.	How many two–digit numbers are divisible by 3?
Answer» 2 digit no divisible by 3 are `12,15,18,21.....,99` let them be `a_1, a_2 , a_3...... `and so on `a_2-a_1= 15-12=3` `a_3-a_2=18-15=3` so,`a=12 & d=3` and we also know last term of series `=99` now,`a_n= a+(n-1)d` `99=12+(n-1)3` `87=(n-1)3` `n=30` `99 `is the 30th term `:.` total terms are 30 answer

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