GATE CSE 2017 Set 1 | Question: 47

Question

The number of integers between $1$ and $500$ (both inclusive) that are divisible by $3$ or $5$ or $7$ is ____________ .

Comments

@Sanjay Sharma can you give an example to support your point and why we should not use floor??

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@abir_banerjee e.g total numbers  divisible by 7 between 6 and 498 are 71  (first if 7 and last is 497 ) but  floor[(498-6)/7] will give 70 

and if we use a.p,. formula

7+(n-1)7=497 gives n=71

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this Question can also be solved using a probability approach. See this variant https://gateoverflow.in/314348/gate-cse-1995-question-25b, and check out the answer by @techbd123 and read in his comments, to know.

Answer 1

i want to add something here if it was 3 and 5 and 7 then answers is 500-271 = 229 there are many kind of similar question in PYQ you al can check thank you.