Bank Exam Time & Work + Pipes & Cisterns – Page 7 (Premium Guide)
Efficiency • LCM Method • Combined Work • Exam Strategy
Core Concept
Work = Efficiency × Time
If A completes work in a days:
Efficiency of A = 1/a
Basic Formula
If A = a days, B = b days Together = (a × b) / (a + b)
LCM Method (Fastest Technique)
Take total work = LCM of given days
Practice Questions
Q1. A = 6 days, B = 12 days
= (6 × 12)/(6 + 12)
= 72/18 = 4 days
Q2. A = 8 days, B = 8 days
= 64/16 = 4 days
Q3. A = 4 days, B = 6 days
= 24/10 = 2.4 days
Q4. A = 5 days, B = 10 days
= 50/15 = 3.33 days
Q5. A = 3 days, B = 6 days
= 18/9 = 2 days
Three Persons Formula
T = abc / (ab + bc + ca)
Q6. A=4, B=6, C=12
= 288 / (24+72+48)
= 288/144 = 2 days
Efficiency Concept
Q7. A is twice as fast as B
Ratio = 2 : 1
Q8. A = 10 days
B = 20 days
Pipes & Cisterns
Same concept as Time & Work
Q9. Pipe A fills in 6 hrs, B in 12 hrs
= 4 hrs
Q10. Pipe fills + leak empties
Subtract efficiency
Topper Tips
- Use LCM method for speed
- Convert into efficiency
- Avoid fraction calculations
- Use ratio approach
Exam Strategy
- Solve in 10–20 seconds
- Use direct formula when possible
- Apply LCM method for complex cases
Final Tip
Think in Efficiency → Not Time
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