How many numbers between 11 and 90 are divisible by 7 ?

1.	How many numbers between 11 and 90 are divisible by 7 ?
Answer» The required numbers are 14, 21, 28, 35, .... 77, 84. This is an A.P. with a = 14 and d = (21 - 14) = 7. Let it contain n terms. Then, T_n = 84 => a + (n - 1) d = 84 => 14 + (n - 1) x 7 = 84 or n = 11. Required number of terms = 11.

Answer»

The required numbers are 14, 21, 28, 35, .... 77, 84.

This is an A.P. with a = 14 and d = (21 - 14) = 7.

Let it contain n terms.

Then, T_n = 84 => a + (n - 1) d = 84

=> 14 + (n - 1) x 7 = 84 or n = 11.

Required number of terms = 11.

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