What is the sum of all positive integers up to 1000 which are divisible by 5 and are not divisible by 2 choices :-?

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Question 4 the day: April 21, 2003 The question for the day is from the topic AP and GP. The question is about finding the sum of a series of numbers that are in Arithmetic Progression

Question

Correct Answer is 50,000 and Correct Choice is (4)

Explanatory Answer The positive integers, which are divisible by 5, are 5, 10, 15, ..., 1000 Out of these 10,20,30,.... 1000 are divisible by 2 Thus, we have to find the sum of the positive integers 5, 15, 25, ...., 995 If n is the number of terms in it the sequence then 995 = 5 + 10(n - 1) => 1000 = 10n Therefore, n = 100. Thus the sum of the series = (n/2)(a + l) = (100/2) (5 + 995) = 50000.

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