Question

how many no.s of 2 digits are divisible by 7?​

Answer 1

We observe that 14 is the first two-digit number divisible by 7 and 98 is the last two-digit number divisible by 7. Thus, we have to determine the number of terms in the sequence.14,21,28,...,98Clearly, it is an A.P. with first term =14 and common difference =7 i.e. a=14 and d=7.Let this be the n th term in this A.P. Then, n th term =98⟹14+(n−1)×=98⟹14+7n−7=98⟹7n=91⟹n=13Hence, there are 13 numbers of two digits which are divisible by 7.

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