POM – WORK MEASUREMENT (Time Study)
Integrated Questions with Solved Answers
Question 1
A job was observed for 8 minutes. The worker’s performance rating is 120% and allowances are 12%. Find the Normal Time (NT) and Standard Time (ST).
Solution
Given: OT = 8 min, Rating = 1.2, Allowance = 0.12
Normal Time: NT = OT × Rating = 8 × 1.2 = 9.6 min
Standard Time: ST = NT ÷ (1 − Allowance) = 9.6 ÷ 0.88 = 10.91 min
Answer: NT = 9.6 min, ST = 10.91 min
Question 2
On a lathe machine, manual time is 4 minutes and machine time is 6 minutes. The operator rating is 110% and allowances are 10%. Find the Standard Time.
Solution
Given: Manual OT = 4 min, Machine time = 6 min, Rating = 1.1, Allowance = 0.10
Manual Normal Time: 4 × 1.1 = 4.4 min
Machine Time (no rating): 6 min
Total Normal Time: NT = 4.4 + 6 = 10.4 min
Standard Time: ST = 10.4 ÷ 0.90 = 11.56 min
Answer: ST = 11.56 min
Question 3
The observed time per unit is 5 minutes. The rating factor is 120% and total allowances are 33%. Calculate the Standard Time.
Solution
Given: OT = 5 min, Rating = 1.2, Allowance = 0.33
Normal Time: NT = 5 × 1.2 = 6 min/unit
Standard Time: ST = 6 ÷ 0.67 = 8.96 min/unit
Answer: ST = 8.96 min/unit
Question 4
Using the data from Question 3, find the Standard Production per 8‑hour shift.
Solution
Shift time: 8 hours = 480 minutes
Standard Production: = 480 ÷ 8.96 = 53.6 ≈ 54 units/shift
Answer: 54 units per shift
Question 5
Explain why Standard Time is calculated by division and not by addition of allowance.
Answer
Allowances represent a percentage of total working time lost to fatigue, personal needs, and delays. Therefore, allowance must be added proportionally to Normal Time. This is correctly done by:
ST = NT ÷ (1 − Allowance)
Adding allowance directly (ST = NT + Allowance) is incorrect because it does not account for the percentage being part of the total time.
One‑Look Formula Sheet
- Normal Time (NT) = OT × Rating
- Standard Time (ST) = NT ÷ (1 − Allowance)
- Standard Production = Available Time ÷ ST
Exam Tips
- Apply rating only to manual time
- Do not rate machine time
- Always convert percentages to decimal form
- Never add allowance directly
Sub section
📘 POM – WORK MEASUREMENT
(Time Study, Standard Time & Standard Production)
1️⃣ BASIC DEFINITIONS (Foundation)
🔹 Observed Time (OT)
- Time measured directly using stopwatch.
- Depends on worker speed.
🔹 Performance Rating (RF)
- Adjusts worker speed to normal performance.
- 120% → worker faster than normal
RF = \frac{120}{100} = 1.2
🔹 Normal Time (NT)
- Time required by a normal worker.
NT = OT \times RF
🔹 Allowances
- Extra time for:
- Fatigue
- Personal needs
- Unavoidable delays
- Added indirectly, not by simple addition.
🔹 Standard Time (ST)
- Time allowed to complete a job including allowances.
ST = \frac{NT}{1 - \text{Allowance}}
2️⃣ IMPORTANT RULES (Very Common Exam Errors)
❌ ST = NT + Allowance → WRONG
✅ ST = NT ÷ (1 − Allowance) → CORRECT
❌ Apply rating to machine time → WRONG
✅ Apply rating only to manual time → CORRECT
3️⃣ NUMERICAL – 1
(Observed Time → NT → ST)
Given
- OT = 8 min
- Rating = 120% = 1.2
- Allowance = 12% = 0.12
Solution
Normal Time
NT = 8 \times 1.2 = 9.6 \text{ min}
Standard Time
ST = \frac{9.6}{1 - 0.12} = \frac{9.6}{0.88} = 10.91 \text{ min}
✅ Answer
- NT = 9.6 min
- ST = 10.91 min
4️⃣ NUMERICAL – 2
(Machine + Manual Time)
Given
- Manual time = 4 min
- Machine time = 6 min
- Rating = 110% = 1.1
- Allowance = 10% = 0.10
Solution
Manual Normal Time
4 \times 1.1 = 4.4 \text{ min}
Machine Time (no rating)
6 \text{ min}
Total Normal Time
NT = 4.4 + 6 = 10.4 \text{ min}
Standard Time
ST = \frac{10.4}{0.90} = 11.56 \text{ min}
✅ Answer
- NT = 10.4 min
- ST = 11.56 min
5️⃣ NUMERICAL – 3 : Standard Production per Shift
Given
- Observed Time (OT) per unit = 5 min
- Rating = 120% = 1.2
- Allowance = 33½ % = 0.335
- Shift Time = 8 hrs = 480 min
Step-1: Normal Time (NT)
\text{Normal Time} = \text{Observed Time} \times \text{Rating}
NT = 5 \times 1.2 = \boxed{6 \text{ min}}
Step-2: Standard Time (ST)
\text{Standard Time} = NT \times (1 + \text{Allowance})
ST = 6 \times (1 + 0.335)
ST = 6 \times 1.335 = \boxed{8.01 \text{ min/unit}}
Step-3: Standard Production per Shift
\text{Standard Production} = \frac{\text{Total Shift Time}}{\text{Standard Time per unit}}
= \frac{480}{8.01}
= \boxed{59.9 \approx 60 \text{ units per shift}}
✅ Final Answer
Standard Production per Shift = 🔹 60 units
🔑 Key Concept (Exam Tip)
- Normal Time adjusts worker speed
- Standard Time adjusts fatigue & delays
- Production = Available Time ÷ Standard Time
6️⃣ ONE-LOOK FORMULA SHEET (REVISION)
NT = OT \times Rating
ST = \frac{NT}{1 - Allowance}
\text{Production per shift} = \frac{\text{Shift time}}{ST}
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