ORS by Vimal

🚀 ULTIMATE IE & OR REVISION (SMART + MEMORY MODE)

🔥 1. PERT & CPM (Most Scoring Area)

📌 Core Logic (Remember This Chain)

• Activity time → Beta distribution
• Project time → Normal distribution (via CLT)

👉 Central idea: explains why total duration becomes normal.

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📊 Key Formula Block

Use this whenever solving numericals:

• Variance:

\sigma^2 = \left(\frac{t_p - t_o}{6}\right)^2

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🎯 Exam Traps

• Critical path = Longest time path (not shortest)
• Slack = 0 → Critical
• Crashing:
  • Single CP → crash that path
  • Multiple CP → crash all paths simultaneously

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⚡ 2. Linear Programming (LPP)

📌 Golden Rules

• Solution lies at corner points
• Alternate optimum → 0 in reduced cost row
• Unbounded → No upper bound

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📊 Duality Shortcut

• Max ↔ Min
• ≤ ↔ ≥
• Coefficients transpose

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🔁 3. Queuing Theory (Formula Heavy)

📌 Core Relations

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🎯 M/M/1 Quick Memory Table

Concept	Formula
Utilization	ρ = λ/μ
Queue length
Waiting time

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⚠️ Shortcut Insight

• If λ ≈ μ → System unstable
• Always check: ρ < 1

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📦 4. Inventory (High Probability Questions)

📌 EOQ Core Formula

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🎯 Key Concepts

• EOQ ignores shortages
• JIT → Batch size = 1
• MRP → derived from MPS

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🏭 5. Production Systems (Theory = Direct Marks)

📊 Memory Table

Type	Key Feature
Job Shop	High variety
Mass Production	High volume
Product Layout	Line balancing
Fixed Layout	Aircraft

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📈 6. Forecasting

📌 Core Formula

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🎯 Insight

• High α → fast reaction
• Low α → smooth/stable

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📊 7. Quality Control

📌 Important Charts

Chart	Use
p-chart	Defective %
c-chart	Defects count

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📌 Control Limit Formula

UCL = \bar{p} + 3\sqrt{\frac{\bar{p}(1-\bar{p})}{n}}

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🔧 8. Reliability

📌 Key Logic

• Series → multiply
• Parallel → use complement

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📊 Maintainability Formula

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💰 9. Engineering Economy

📌 Must-Remember

• Straight line → constant depreciation
• SYD → decreasing depreciation

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📊 Capital Recovery

CR = P(A/P,i,n)

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🧠 10. Learning Curve

📌 Core Model

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🎯 Shortcut

• 80% curve → time reduces to 80% on doubling

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⚡ 11. Super Fast Revision (30 सेकंड में पूरा OR)

👉 PERT → Beta → Normal
👉 CPM → Longest path
👉 LPP → Corner points
👉 Queue → ρ < 1
👉 EOQ → Balance cost
👉 JIT → 1 unit
👉 Quality → 3σ limits
👉 Reliability → Series ×, Parallel complement
👉 Forecast → α decides speed

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🎯 FINAL EXAM STRATEGY (VERY IMPORTANT)

Since you’re preparing seriously (UPSC + M.Tech mindset):

✅ Do This:

• Revise this sheet 3 times
• Solve PYQs immediately after each topic
• Focus on:
  • PERT/CPM numericals
  • LPP graphical/simplex
  • Queue formulas

❌ Avoid:

• Over-reading theory
• Memorizing without solving

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