Multiple choice

4 pipes can fill a reservoir in 15, 20, 30 and 60 hours respectively. The first was opened at 6 am, second at 7 am third at 8 am and fourth at 9 am. When will the reservoir be full? 4 पाइप क्रमशः 15, 20, 30 और 60 घंटे में एक जलाशय भर सकते हैं। पहला सुबह 6 बजे खुलता था, दूसरा सुबह 7 बजे, तीसरा सुबह 8 बजे और चौथा सुबह 9 बजे खोला गया । जलाशय कब पूरा भर जाएगा?

  1. 11 am

  2. 12 pm

  3. 12: 30 pm

  4. 1.00 pm

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The combined rate of all 4 pipes is 1/15 + 1/20 + 1/30 + 1/60 = 1/6 per hour. Work done by 9am: pipe1 works 3 hours (3/15), pipe2 works 2 hours (2/20), pipe3 works 1 hour (1/30), totaling 1/3. Remaining 2/3 work takes 4 hours at combined rate. 9am + 4 hours = 1pm.