Multiple choice

Henning Holck-Larsen cold-drink fountain is being filled by Fanta and Coke in 20 min and 60 min, respectively. At a particular instant of time, both the pipes are opened. After 12 minutes, Fanta pipe is closed. Total time taken to fill the fountain is:

  1. 4 minutes

  2. 14 minutes

  3. 24 minutes

  4. 29 minutes

  5. 60 minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fanta rate = 1/20, Coke rate = 1/60. Fanta works for 12 mins: 12 * (1/20) = 12/20 = 3/5 of the tank. Remaining = 2/5. Coke rate = 1/60. Time for Coke to finish = (2/5) / (1/60) = 24 minutes. Total time = 24 minutes.

AI explanation

In 12 minutes, Fanta fills 12/20 of the fountain and Coke fills 12/60, leaving 1 minus 3/5 minus 1/5, which is 1/5 of the fountain to be filled. Coke alone takes 60 minutes, so it needs 60 multiplied by 1/5 minutes to finish, taking 12 more minutes. Adding the initial 12 minutes to the remaining 12 minutes gives a total time of 24 minutes.

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