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📊 Math
Q. Pipe A can fill a tank in 30 hours. Pipe B can fill it in 60 hours. Pipe C empties it in 20 hours. If all are opened together, the tank will be filled in?
  • (A) 30 hours
  • (B) 60 hours
  • (C) No filling
  • (D) 120 hours
💬 Discuss
✅ Correct Answer: (C) No filling

Explanation: Net rate = 1/30 + 1/60 − 1/20 = 0.

📊 Math
Q. Two inlet pipes can fill a tank in 6 and 8 hours respectively. An outlet pipe can empty it in 12 hours. How long will the tank take to fill if all pipes are opened?
  • (A) 4 hours
  • (B) 5 hours
  • (C) 6 hours
  • (D) 8 hours
💬 Discuss
✅ Correct Answer: (C) 6 hours

Explanation: Net rate = 1/6 + 1/8 − 1/12 = 1/6.

📊 Math
Q. A tank can be filled by two pipes in 10 and 15 hours respectively. Due to a leak, the tank takes 30 hours to fill. In how many hours can the leak empty the full tank?
  • (A) 20 hours
  • (B) 30 hours
  • (C) 60 hours
  • (D) 45 hours
💬 Discuss
✅ Correct Answer: (B) 30 hours

Explanation: Leak rate = (1/10 + 1/15) − 1/30 = 1/30.

📊 Math
Q. Pipe A fills a tank in 5 hours and pipe B empties it in 10 hours. If both are opened together, how long will it take to fill the tank?
  • (A) 5 hours
  • (B) 10 hours
  • (C) 15 hours
  • (D) No filling
💬 Discuss
✅ Correct Answer: (B) 10 hours

Explanation: Net rate = 1/5 − 1/10 = 1/10.

📊 Math
Q. Two pipes can fill a tank in 4 hours and 6 hours respectively. If both are opened for 2 hours and then the faster pipe is closed, how much time will the slower pipe take to fill the remaining tank?
  • (A) 1 hour
  • (B) 2 hours
  • (C) 3 hours
  • (D) 4 hours
💬 Discuss
✅ Correct Answer: (B) 2 hours

Explanation: Work done in 2 hours = 2(1/4+1/6)=5/6. Remaining=1/6 → slower pipe (1/6 per hour) takes 1 hour.

📊 Math
Q. Pipe A can fill a tank in 7 hours and pipe B can empty it in 14 hours. If both are opened together, the tank will be filled in?
  • (A) 7 hours
  • (B) 10.5 hours
  • (C) 14 hours
  • (D) 21 hours
💬 Discuss
✅ Correct Answer: (C) 14 hours

Explanation: Net rate = 1/7 − 1/14 = 1/14.

📊 Math
Q. A pipe fills a tank in 18 hours. Due to a leak at the bottom, it is filled in 24 hours. In how many hours can the leak empty the tank?
  • (A) 48 hours
  • (B) 72 hours
  • (C) 36 hours
  • (D) 24 hours
💬 Discuss
✅ Correct Answer: (B) 72 hours

Explanation: Leak rate = 1/18 − 1/24 = 1/72.

📊 Math
Q. Two pipes fill a tank in 20 hours and 30 hours respectively. If both are opened together, after how many hours will half the tank be filled?
  • (A) 6 hours
  • (B) 7.5 hours
  • (C) 8 hours
  • (D) 10 hours
💬 Discuss
✅ Correct Answer: (B) 7.5 hours

Explanation: Net rate = 1/20 + 1/30 = 1/12 → half tank in 6 hours.

📊 Geography
Q. A can do a work in 24 days. B can do it in 16 days. In how many days will they complete the work together?
  • (A) 8 days
  • (B) 9 days
  • (C) 10 days
  • (D) 12 days
💬 Discuss
✅ Correct Answer: (B) 9 days

Explanation: 1/24 + 1/16 = 5/48 → time = 48/5 ≈ 9 days.

📊 Geography
Q. A can do a work in 15 days. B can do it in 20 days. C can do it in 30 days. In how many days will they complete it together?
  • (A) 5 days
  • (B) 6 days
  • (C) 7 days
  • (D) 10 days
💬 Discuss
✅ Correct Answer: (B) 6 days

Explanation: 1/15 + 1/20 + 1/30 = 9/60 = 3/20 → time = 20/3 ≈ 6 days.

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