EOQ for dMAT: Business Reasoning Guide

The official dMAT General Academic Module sample includes Optimal Order Quantity, also known as EOQ. This matters because it proves Part 2 is not only mathematics or engineering. It can also test business reasoning, model assumptions, variable relationships, and graph interpretation.

Use this page after the dMAT General Academic Module guide and the dMAT preparation guide.

Last reviewed: 9 October 2026. This article is based on the official General Academic Module preparatory material (edition as at 2 September 2026). All practice questions below are Think Mile original and are not official dMAT questions.

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Direct Answer

For dMAT, study EOQ as a model-reading topic:

• what an inventory model is;
• constant demand assumptions;
• ordering cost;
• holding cost;
• average inventory;
• trade-off between ordering often and storing too much;
• interpreting a cost graph;
• understanding square-root relationships;
• predicting what happens when a variable increases or decreases.

You do not need a full operations-management course. You need enough model literacy to read a passage, identify assumptions, and apply the formula or graph.

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Official Evidence

The official General Academic Module sample includes an Optimal Order Quantity exercise with seven questions. The task introduces a business model, explains assumptions and variables, and then asks students to use the model.

The sample shows that Part 2 can ask for:

Important limitation: EOQ is officially shown in the sample, but it is not guaranteed as a real-exam topic.

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Concept Lesson

What is EOQ?

EOQ stands for Economic Order Quantity. It answers a simple business question:

How much should a company order each time so that inventory-related costs are low?

If a company orders very small amounts, it must place orders often. That increases ordering cost.

If a company orders very large amounts, it stores more inventory. That increases holding cost.

EOQ balances these two costs.

Ordering cost

Ordering cost is the cost of placing or processing an order. It may include administration, delivery setup, purchasing work, or supplier processing.

If order size is small, the company orders more often, so total ordering cost usually rises.

Holding cost

Holding cost is the cost of keeping inventory in storage. It may include warehouse space, insurance, capital tied up in stock, spoilage, or risk of obsolescence.

If order size is large, average inventory rises, so holding cost usually rises.

Average inventory

In a simple EOQ model, inventory starts high after an order arrives and falls as demand uses it. Average inventory is often half the order quantity.

If order quantity is Q, average inventory is often modelled as:

Q / 2

Model assumptions

Basic EOQ often assumes:

• demand is known and constant;
• order cost is constant;
• holding cost is constant;
• no quantity discount;
• replenishment is predictable.

If a question gives a scenario where these assumptions fail, the model may no longer fit well.

Square-root relationship

EOQ formulas often include a square root. That means changes are not one-to-one.

For example, if one variable becomes four times larger inside the square root, EOQ may double, not become four times larger.

This is a common dMAT-style reasoning point: understand direction and scale, not just plug in numbers.

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Worked Example

Think Mile original example:

A shop sells 1,200 notebooks per year. It pays EUR 20 each time it places an order. Holding one notebook in inventory costs EUR 2 per year.

A simplified EOQ formula is:

EOQ = sqrt((2DS) / H)

where:

• D = annual demand;
• S = ordering cost per order;
• H = holding cost per unit per year.

Question: what is the EOQ?

Solution:

EOQ = sqrt((2 x 1200 x 20) / 2)

EOQ = sqrt(24000)

EOQ is about 155.

Answer: the shop should order about 155 notebooks per order under this simplified model.

Reading skill tested: identify the variables from the passage and substitute them into the supplied formula.

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Common Traps

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Think Mile Original Practice

Passage

A cafe uses a simple inventory model for coffee beans. Demand is constant at 600 bags per year. Each order has a fixed processing cost. Each bag kept in storage has a yearly holding cost.

The model uses:

EOQ = sqrt((2DS) / H)

where D is annual demand, S is ordering cost per order, and H is holding cost per bag per year.

Questions

1. If annual demand increases while S and H stay the same, what happens to EOQ?

A. It decreases
B. It increases
C. It must become zero
D. It becomes unrelated to demand

2. If holding cost increases while D and S stay the same, what happens to EOQ?

A. It decreases
B. It increases
C. It doubles automatically
D. It is unchanged

3. Why is ordering a very small quantity not always best?

A. It can require too many orders and raise ordering cost.
B. It always makes holding cost infinite.
C. It removes demand.
D. It makes inventory assumptions irrelevant.

4. If D = 800, S = 25, and H = 4, what value is inside the square root?

A. 100
B. 1,000
C. 10,000
D. 40,000

Solutions

1. B. Demand is in the numerator. If demand increases, EOQ increases, although the square-root form means it does not increase one-to-one.

2. A. Holding cost is in the denominator. If holding cost increases, EOQ decreases.

3. A. Very small order quantities mean the cafe must place orders more often.

4. C. (2 x 800 x 25) / 4 = 40,000 / 4 = 10,000.

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Graph Interpretation

EOQ passages may include a graph with order quantity on the horizontal axis and cost on the vertical axis.

Typical pattern:

• ordering cost decreases as order quantity increases;
• holding cost increases as order quantity increases;
• total cost has a minimum point.

The EOQ is usually near the point where total cost is lowest. In a graph question, do not choose the smallest order size or the largest order size automatically. Look for the minimum of total cost.

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Timed Strategy

When an EOQ or business-model passage appears:

1. Identify the model assumptions.
2. Label each variable in the formula.
3. Ask whether the question needs calculation, graph reading, or direction-of-change reasoning.
4. Estimate direction before calculating.
5. Eliminate answers that violate the assumptions.

This is useful beyond EOQ. The same method works for other business, economics, and operations passages.

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Free Learning Path

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Official vs Think Mile Recommendation

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Frequently Asked Questions

Do I need to memorise the EOQ formula?
Not as a guaranteed requirement. The official sample uses supplied material, but the safest skill is knowing how to read and apply a formula quickly.

Is EOQ only for business students?
No. The APS India General Academic Module is cross-disciplinary. Any affected candidate may need to reason through a business-style model.

What is the biggest EOQ trap?
Ignoring assumptions. A model answer can be wrong if the scenario violates constant demand, no discounts, or other assumptions.

Should I study all operations management topics?
No. Start with EOQ-style model reading, graphs, cost trade-offs, and variable relationships.

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Source note: This article was reviewed against the official General Academic Module preparatory material, the official dMAT India page, Business LibreTexts inventory resources, and Khan Academy proportional-reasoning material. Think Mile is not affiliated with APS India or g.a.s.t.; all practice content here is original.