On a 200 m long straight road, maximum number of poles are fixed at 20 m interval. How many of these poles should be removed in order to have maximum number of poles at an interval of 40 m on the road?

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CSIR-UGC (NET) Mathematical Science: Held on (26 Nov 2020)
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  1. 8
  2. 6
  3. 5
  4. 4

Answer (Detailed Solution Below)

Option 3 : 5
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Detailed Solution

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Calculation:

When poles are placed at 20 m interval, numbers of poles that can be placed = 200/20 + 1(Pole is also placed at 0 m)

= 11 poles.

Now, when poles are placed at 40 m interval, numbers of poles that can be placed = 200/40 + 1(Pole is also placed at 0 m)

= 6 poles.

∴ Number of poles removed = 11 - 6 = 5 poles.

The correct answer is Option 3.

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