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प्रश्न
How many three digit numbers are divisible by 7?
उत्तर
The first three digit number which is divisible by 7 is 105 and the last digit which is divisible by 7 is 994.
This is an A.P. in which a = 105, d = 7 and tn = 994.
We know that nth term of A.P is given by
tn = a + (n – 1)d
`\implies` 994 = 105 + (n – 1)7
`\implies` 889 = 7n – 7
`\implies` 896 = 7n
`\implies` n = 128
∴ There are 128 three digit numbers which are divisible by 7.
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