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Solution - How many three digit numbers are divisible by 7 - CBSE Class 10 - Mathematics

Conceptnth Term of an AP

Question

How many three digit numbers are divisible by 7

Solution

First three-digit number that is divisible by 7 = 105

Next number = 105 + 7 = 112

Therefore, 105, 112, 119, …

All are three digit numbers which are divisible by 7 and thus, all these are terms of an A.P. having first term as 105 and common difference as 7.

The maximum possible three-digit number is 999. When we divide it by 7, the remainder will be 5. Clearly, 999 − 5 = 994 is the maximum possible three-digit number that is divisible by 7.

The series is as follows.

105, 112, 119, …, 994

Let 994 be the nth term of this A.P.

a = 105

d = 7

an = 994

n = ?

an = a + (n − 1) d

994 = 105 + (n − 1) 7

889 = (n − 1) 7

(n − 1) = 127

n = 128

Therefore, 128 three-digit numbers are divisible by 7.

Is there an error in this question or solution?

APPEARS IN

 NCERT Mathematics Textbook for Class 10 (with solutions)
Chapter 5: Arithmetic Progressions
Q: 13 | Page no. 106

Reference Material

Solution for question: How many three digit numbers are divisible by 7 concept: null - nth Term of an AP. For the course CBSE
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