This set has eleven original questions, ordered from easier to harder, covering all five lessons in operations and productivity. Questions 1 and 2 practise production methods, 3 to 5 productivity, 6 and 7 bottlenecks, 8 and 9 quality control, and 10 and 11 inventory and mixed reasoning.
All businesses here are fictional.
Write each answer on paper, with units, then open the answer. Note which ones you missed and use the routing list at the end. A short record in the mistake log and retest queue helps you retry a fresh question later, and the ratios tool can check a division or percentage.
Questions
1. Name the production method used in each case: (a) A carpenter in Ipoh builds one wardrobe to a customer’s drawings. (b) A bakery makes 200 pandan buns, then cleans the trays and makes 200 kaya buns. (c) A bottling plant fills one size of mineral water bottle continuously.
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(a) Job production: one item made to order. (b) Batch production: a group of identical items, then a reset before the next group. (c) Flow production: one standard product made continuously.
2. A cookie house makes three flavours. Each batch takes 80 minutes, and the oven is cleaned for 20 minutes between batches. Calculate the time to make one batch of each flavour, then the time if there are four flavours and the oven is also cleaned after the last batch.
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Three flavours: 3 × 80 = 240 minutes, plus 2 cleaning breaks of 20 minutes, which is 40. Total: 280 minutes (4 hours 40 minutes).
Four flavours with cleaning after every batch: 4 × 80 = 320, plus 4 × 20 = 80. Total: 320 + 80 = 400 minutes (6 hours 40 minutes).
3. A factory made 7,200 units with 12 workers. Calculate labour productivity.
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7,200 ÷ 12 = 600 units per worker. Check: 12 × 600 = 7,200.
4. The next month the same factory made 7,800 units with 13 workers. The owner says, “Output rose, so productivity rose.” Is the owner right?
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Productivity: 7,800 ÷ 13 = 600 units per worker, the same as before. Total output rose by 600 ÷ 7,200 = 8.3%, but the workforce grew by the same proportion (1 ÷ 12 = 8.3%). The owner is not right: output rose, productivity stayed at 600.
5. After staff training, output per worker per week rose from 50 units to 56 units. Calculate the percentage change in productivity.
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Change = 56 − 50 = 6. Percentage change = 6 ÷ 50 × 100 = 12%.
6. A tauhu factory has four stages with these capacities per hour: soaking 400, grinding 260, pressing 300 and packing 350. Identify the bottleneck and calculate output in an 8-hour shift.
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The lowest capacity is grinding at 260 per hour, so grinding is the bottleneck. Output: 260 × 8 = 2,080 units per shift.
7. The tauhu owner buys a second grinder and doubles grinding capacity to 520 per hour. Find the new bottleneck, the new shift output and the gain.
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Capacities are now 400, 520, 300 and 350. The lowest is pressing at 300, so pressing is the new bottleneck. New output: 300 × 8 = 2,400. Gain: 2,400 − 2,080 = 320 units per shift. It is less than the doubling might suggest, because pressing now limits the line.
8. An inspector tests 50 bottles from a batch of 2,000 and finds 4 faulty. The firm’s limit is 5%. Calculate the sample fault rate, estimate the faulty bottles in the batch and state whether the batch passes.
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Fault rate: 4 ÷ 50 = 0.08, or 8%. Estimate: 0.08 × 2,000 = 160 bottles. The 8% rate is above the 5% limit, so the batch fails and should be held for further checking.
9. At the end of a packing line, a worker weighs every tenth bag of rice, and any bag below the stated weight is removed and refilled. Explain this quality-control step.
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The check: every tenth bag is weighed at the end of the line, so about 10% of bags are sampled. The standard: the weight stated on the label. The action: an underweight bag is removed and refilled before it is sold. The effect: a benefit is that customers receive the weight they pay for, which protects trust. A cost is the worker’s time and the delay in refilling. Sampling is cheaper than weighing every bag, but a few underweight bags between checks may be missed.
10. A grocery uses 1,000 tins of tomato paste a month. Option 1: one order of 1,000 tins at RM2.00 each. Option 2: two orders of 500 tins a month at RM2.05 each. The store room holds 600 tins. Calculate the monthly cost of each and recommend an option.
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Option 1: 1,000 × 2.00 = RM2,000. Option 2: each order is 500 × 2.05 = RM1,025, so two orders cost RM2,050. Option 1 is RM50 cheaper, but it needs space for 1,000 tins and the room holds 600. It does not fit. Recommend Option 2, because 500 tins fit. If the grocery could store 1,000 tins safely at a cost below RM50 a month, Option 1 would win.
11. A kuih factory makes 1,800 boxes a week with 6 workers. It buys a steaming machine, and output rises to 2,400 boxes a week with the same 6 workers. Calculate the productivity before and after, the percentage change, and write one sentence of interpretation.
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Before: 1,800 ÷ 6 = 300 boxes per worker. After: 2,400 ÷ 6 = 400 boxes per worker. Change: 100, so 100 ÷ 300 × 100 = 33.3%. Interpretation: each worker produces a third more boxes with the machine, so the cost of the machine should be compared with the extra output it brings.
If you got these wrong
- Questions 1 and 2: you may have chosen a method from the quantity alone or miscounted the cleaning breaks. Return to comparing job, batch and flow methods.
- Questions 3 to 5 and 11: you may have divided by the wrong figure or used total output. Return to calculating productivity from supplied data.
- Questions 6 and 7: you may have sped up a stage that was not the lowest. Return to identifying a bottleneck in a process.
- Questions 8 and 9: you may have left out the standard or the action. Return to explaining a quality-control step.
- Question 10: you may have picked the cheaper option without checking space. Return to comparing inventory choices using stated constraints.
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