ZestExam

SSC CPO Efficiency Problems

Study Material — 2 PYQs (2020–2020) · Concept Notes · Shortcuts

SSC CPO Efficiency Problems is a frequently tested subtopic — 2 previous year questions from 2020–2020 papers are included below with concept notes, key rules and shortcut tricks.

2 PYQs

2020–2020

0 Practice

MCQs

8 Key Points

to remember

Free

no login needed

Take Free Mock →

Also for:CGL CHSL MTS GD

PYQs

2

Practice

0

Key Points

8

Access

Free

Previous Year Questions

SSC CPO Efficiency Problems — Past Exam Questions

2 questions from actual SSC CPO papers · all shown free · click option to reveal solution

Exam Q 12020Previous Year Pattern

A's efficiency is 25% more than B's. If A and B together complete a task in 9 days, how many days does B alone need to complete the task?

Test Efficiency Problems under exam conditions

Free SSC CPO mock · instant rank · no login

Free Mock →

Exam Q 22020Previous Year Pattern

A team of workers can complete a project in 30 days. After 10 days of work, the team's efficiency increases by 25%. The project is then completed in 12 more days. If the project had been completed at the original efficiency throughout, how many days would it have taken?

Concept Notes

Efficiency Problems— Rules & Concept

💡

Core Concept

Read this first — the foundation of the topic

Efficiency in Time & Work represents how much work a person can complete in unit time. Think of efficiency as work rate or speed of work. If Ram can finish a job in 10 days, his efficiency is 1/10 of the total work per day.

This concept forms the backbone of most SSC CGL Time & Work problems. Key Rules: Total Work = Efficiency × Time. When workers combine, their efficiencies add up. If A's efficiency is 1/12 and B's efficiency is 1/15, together they work at (1/12 + 1/15) efficiency.

The reciprocal of combined efficiency gives combined time.

🔢

Formula Block

Memorise — at least one formula appears in every paper

Individual Efficiency = 1/Time taken. Combined Efficiency = Sum of individual efficiencies. Time for combined work = 1/Combined Efficiency. Work Ratio = Efficiency Ratio = Inverse of Time Ratio.

📊

Exam Patterns

What examiners ask — read before attempting PYQs

→Common types include

workers joining/leaving at different times, comparing work rates, finding individual efficiencies when combined time is given, and efficiency ratios. Questions often involve 2-3 workers with fractional efficiencies

⚡Powerful Shortcut

LCM Method. Take LCM of all given times as total work units. Each person's efficiency becomes LCM/their time. This eliminates fractions completely and makes calculations super fast.

✏️

Worked Example

Solve this step-by-step before moving on

1

Step 1

Find LCM of 15 and 20 = 60 (assume total work = 60 units)

2

Step 2

A's efficiency = 60/15 = 4 units per day

3

Step 3

B's efficiency = 60/20 = 3 units per day

4

Step 4

Combined efficiency = 4 + 3 = 7 units per day

5

Step 5

Combined time = 60/7 = 8(4/7) days Alternative method: A's efficiency = 1/15, B's efficiency = 1/20. Combined = 1/15 + 1/20 = (4+3)/60 = 7/60. Time = 1/(7/60) = 60/7 days. Another Trick: For two workers, combined time = (Product of individual times)/(Sum of individual times). Here: (15×20)/(15+20) = 300/35 = 60/7 days. Common Mistake: Students often forget that when efficiency increases, time decreases proportionally. Also, they add times instead of adding efficiencies when workers combine. Remember: efficiencies add up, not times.

Key Points to Remember

Efficiency = 1/Time taken by individual worker
When workers combine, their efficiencies get added
Combined time = 1/(Sum of individual efficiencies)
Work ratio equals efficiency ratio equals inverse of time ratio
LCM method eliminates fractions and speeds up calculations
For two workers: Combined time = (Product of times)/(Sum of times)
Higher efficiency means lower time taken for same work
Total work = Efficiency × Time for any worker

Exam-Specific Tips

Combined efficiency formula for two workers: 1/T1 + 1/T2
Work ratio formula: W1:W2 = E1×t1 : E2×t2
Efficiency is always expressed as fraction of total work per unit time
When efficiency doubles, time becomes half for same work
LCM method: Total work = LCM of all given individual times
Two workers formula: Combined time = (T1×T2)/(T1+T2)
If A is twice as efficient as B, then A:B efficiency ratio = 2:1
Efficiency and time are inversely proportional for same work

60-Second Revision — Efficiency Problems

Remember: Efficiencies add up when workers combine, times don't
Formula: Combined time for two workers = (T1×T2)/(T1+T2)
Trick: Use LCM method to avoid fractions in calculations
Trap: Don't confuse work ratio with time ratio - they're inverse
Quick check: Higher efficiency always means lower time
Pattern: Most SSC questions involve 2-3 workers with simple time values
Shortcut: Efficiency ratio = Inverse of time ratio

Studied the notes? Now test yourself

See how Efficiency Problems appears in the real SSC CPO paper

Full timed mock · Instant All-India percentile · Free

Start Free Mock →Practice Panel

✓ Free forever for basic prep✓ No app download✓ Real exam-pattern questions✓ 12,000+ aspirants