Multiple choice

Three pipes P, Q and R can fill a Cistern in 6 hours. After working at it together for 2 hours, R is closed and P and Q can fill the remaining part in 7 hours. The number of hours taken by R alone to fill the Cistern is तीन पाइप P, Q और R एक हौज को 6 घंटे में भर सकते हैं। 2 घंटे तक इस पर एक साथ काम करने के बाद, R को बंद कर दिया जाता है और P और Q शेष भाग को 7 घंटे में भर सकते हैं। अकेले R द्वारा टंकी को भरने में लिया गया समय है

  1. 12 hours 12 घंटे

  2. 10 hours 10 घंटे

  3. 14 hours 14 घंटे

  4. 18 hours 18 घंटे

  5. None of these इनमें से कोई नहीं
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let total work = 42 units (LCM of 6, 2, 7). Combined rate of P+Q+R = 7 units/hr. In 2 hours, they complete 14 units, leaving 28 units. P+Q fill these in 7 hours, so their combined rate is 4 units/hr. Therefore, R's rate is 7-4 = 3 units/hr. Time for R alone = 42/3 = 14 hours.

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