Lesson 34 of 35 · Data Insights
Multi-Source Reasoning: combining rules, tables and updates
Map what each source contributes, apply a rule from one source to figures in another, and spot updates, conflicts and questions the sources cannot answer.
About 24 minutes
In this lesson
- Map several sources quickly: what each one is, what it defines and what it gives as data.
- Apply a rule stated in one source to the figures in another, step by step.
- Notice when a later source changes or contradicts an earlier one, and when the sources together cannot answer a question.
The idea
What the question type asks
Multi-Source Reasoning is one of the five question types GMAC lists for Data Insights. As the name says, the work is reasoning from more than one source. This lesson practises it with sources of different kinds, such as a memo, a table and an email: combining them, noticing where they disagree, and judging which source is relevant. GMAC states that for Data Insights questions with several parts, all parts must be correct to score.
The checks on this page are single-answer multiple choice, one question each, and almost every one needs facts from at least two sources.
Map the sources before the questions
Do not read every source in full detail first. Skim each one and note, in a few words, three things:
- What it is. A rule, a dataset, an update, an opinion.
- What it defines. Thresholds, conditions, definitions ("a station is flagged when…"). Rules usually live in text.
- What it gives as data. Columns, units, the period covered.
A short map, such as "Memo: qualification rule, two conditions, order frequency. Table: price, delivery charge, on-time rate. Email: order frequency changes next quarter", is enough. When a question comes, the map tells you where to look.
Rules in text, numbers in tables
The most common question applies a rule from a text source to the rows of a table. Treat it as a checklist:
- Write the rule's conditions exactly, including the words that matter: "at most" includes the boundary, "more than" does not; "and" needs every condition, "or" needs only one.
- Find the figures each condition needs. Often one condition needs a value that no single column holds and you must build it, such as a delivery charge spread over the boxes in an order.
- Run every row through every condition and mark pass or fail.
When a rule has an "or", a row can pass on either condition; check the second condition for every row that fails the first. When it has an "and", stop at the first failure.
Updates and conflicts
Sources may disagree, and the disagreement can be the point of the question. A later email may change an assumption the memo made ("from next quarter we order every two weeks"). Then a question can ask about the situation before the change, after it, or the difference. Read the question for which situation it means, and note on your map which source supersedes which.
Other conflicts are real discrepancies: two sources give different values for the same thing. Do not average them or pick the one you like. Look for what the question says about which to use; if it says nothing, it may be asking you to notice that they differ.
What the sources cannot tell you
Some questions ask whether something can be determined. Be strict. A monthly total does not give a busiest day; an on-time rate does not give the number of late deliveries unless the number of deliveries is also known; a rule for "this year" says nothing about last year. If the figure you need is not in any source and cannot be built from them, the answer is that it cannot be determined, however reasonable a guess would be.
Relevance
Not every source matters for every question. Part of the skill is ignoring a source that is beside the point. Before you calculate, ask which sources the question touches. A question about qualification under current terms does not need the email about next quarter, and bringing it in produces a wrong answer.
Working method
- Map the sources in a few words each.
- For each question, list the sources it needs.
- Write the rule's conditions, then compute only the figures they need.
- Check boundaries ("at most", "more than") and connectives ("and", "or").
- Before answering, ask whether a later source changes the picture for the situation the question asks about.
Worked examples
Example 1: Applying a rule from a memo to a table
Source 1, procurement memo. "Our warehouses need 18,000 boxes per quarter. A supplier qualifies only if (a) its cost per box, including delivery, is at most $0.95, and (b) its on-time delivery rate last year was at least 92%. Delivery is charged per order, and we place one order a month, three a quarter, of equal size."
Source 2, supplier table.
| Supplier | Price per box | Delivery charge per order | On-time rate last year |
|---|---|---|---|
| Korra | $0.82 | $600 | 94% |
| Lumen | $0.88 | $150 | 91% |
| Mistral | $0.79 | $1,200 | 96% |
| Norvik | $0.85 | $300 | 93% |
Source 3, email from the warehouse manager. "From next quarter we will order every two weeks instead: six orders a quarter, still 18,000 boxes in total."
Under the current ordering, which suppliers qualify?
The question is about current ordering, so Sources 1 and 2 are needed; Source 3 describes next quarter and does not apply.
Build the missing figure: delivery per box. Three orders a quarter cost , spread over 18,000 boxes, so delivery per box is .
Cost per box: Korra ; Lumen ; Mistral ; Norvik .
Condition (a), at most $0.95: Korra, Lumen and Norvik pass; Mistral fails. Condition (b), at least 92%: Lumen's 91% fails. The rule says "and", so a supplier must pass both.
Answer
Korra and Norvik qualify. Mistral, with the lowest price per box, fails once delivery is included, and Lumen, well within the cost limit at $0.905, fails the on-time condition.
Example 2: An update changes the answer
Using the same three sources, which suppliers qualify next quarter, and how much more will the qualifying supplier's boxes cost per quarter than under monthly ordering?
Source 3 now applies: six orders a quarter, so delivery per box is .
Cost per box: Korra (fails); Lumen (passes on cost, still fails on-time); Mistral (fails); Norvik .
"At most $0.95" includes $0.95 itself, so Norvik passes, and its 93% passes the on-time condition.
Norvik's quarterly cost: monthly ordering ; two-weekly ordering . Check per box: and .
Answer
Only Norvik qualifies, at exactly $0.95 per box, and its boxes cost $900 more per quarter. Reading "at most" as "less than" would wrongly rule out every supplier.
Example 3: What the sources cannot answer
Using the same three sources, can you determine which supplier made the largest number of late deliveries last year?
A number of late deliveries is (1 minus the on-time rate) times the number of deliveries each supplier made last year.
The table gives on-time rates, but no source gives how many deliveries each supplier made last year, to these warehouses or to anyone else.
Without the counts, a supplier with a higher on-time rate could still have more late deliveries, so the ranking cannot be built.
Answer
No, it cannot be determined. Picking Lumen because it has the lowest on-time rate confuses a rate with a count.
Common traps
Using a source the question does not cover
An update that applies "from next quarter" does not change the answer to a question about now, and the other way round. Before you calculate, say which situation the question asks about and which sources describe it.
Misreading the boundary words
"At most $0.95" passes $0.95; "more than 10%" fails exactly 10%. A row can land exactly on a boundary, as Norvik does next quarter above. Write the inequality down with the correct sign.
Treating "or" as "and", or "and" as "or"
A rule with "or" flags a row that meets either condition, so a row that fails the first must still be tested on the second. A rule with "and" needs both, so one failure settles it.
Answering a "can it be determined" question with a guess
If no source gives a needed figure and none can be built from the others, the answer is that it cannot be determined, even when one option looks likely. Rates without counts, totals without daily figures and this year without last year are the usual gaps.
Check yourself
Answer each question before you open its answer.
Question 1: Applying a rule and a budget note
Multi-Source Reasoning
Source A, scheme report. "A bike-share station is flagged for expansion when its average daily trips exceed 1.5 times its number of docks, or when it was empty for more than 10% of operating hours. Stations operate 18 hours a day."
Source B, last month's figures (30 days).
| Station | Docks | Trips in the month | Hours empty in the month |
|---|---|---|---|
| Quay | 20 | 960 | 40 |
| Market | 30 | 1,260 | 60 |
| Park | 16 | 690 | 30 |
| Mill | 24 | 1,170 | 48 |
| Hill | 12 | 510 | 70 |
Source C, budget note. "This year only stations flagged under the trips condition can be expanded; stations flagged only for empty hours will get extra rebalancing instead."
According to the sources, how many of the five stations can be expanded this year?
- A.0
- B.1
- C.2
- D.4
- E.5
Show the answer
Answer: C. 2
Working
Daily trips are monthly trips over 30: Quay 32, Market 42, Park 23, Mill 39, Hill 17. Trips condition, more than 1.5 times docks: Quay yes; Market no; Park no; Mill yes; Hill no. Empty condition, more than 10% of hours, so more than 54 hours: Market (60) and Hill (70). So Source A flags Quay, Market, Mill and Hill, but Source C allows expansion only for stations flagged under the trips condition: Quay and Mill.
Why the other options are wrong
- A. This reads Source A's "or" as "and": no station meets both conditions, but the rule needs only one, and Source C keeps the trips condition.
- B. Mill, at 1.625 trips per dock a day, is not the only station above 1.5: Quay's 32 trips on 20 docks is 1.6.
- D. Four stations are flagged under Source A, but Source C limits expansion to stations flagged under the trips condition, which removes Market and Hill.
- E. This compares daily trips with the number of docks, leaving out the factor 1.5; every station has more daily trips than docks.
What carries over
Apply the rule in one source, then ask whether another source narrows or changes it.
Question 2: What the sources can answer
Multi-Source Reasoning
Using the same three sources, which of the following can be determined?
- A.The number of trips that started at Quay on its busiest day last month
- B.The number of hours Park had every dock full last month
- C.The percentage of last month's operating hours for which Hill was empty
- D.Whether Mill was flagged for expansion in the previous year
- E.The number of trips Market lost while it was empty
Show the answer
Answer: C. The percentage of last month's operating hours for which Hill was empty
Working
Hill was empty for 70 hours, and Source A gives 18 operating hours a day over Source B's 30 days, 540 hours. So the share is . Every other figure needs data that no source holds: daily trips, full hours, last year's figures or demand while empty.
Why the other options are wrong
- A. Source B gives only a monthly total of 960; the daily average of 32 says nothing about the busiest day.
- B. Source B records hours empty, not hours full; nothing in the sources gives full hours.
- D. The sources give only last month's figures; Mill's flag last year cannot be built from them.
- E. Being empty stops bikes being taken, but no source gives how many people wanted a bike during those hours.
What carries over
A figure can be determined only if every input to it appears in, or can be built from, the sources.
Question 3: The smallest total that triggers the rule
Multi-Source Reasoning
Using the same sources, suppose Park keeps its 16 docks and next month also has 30 days. What is the smallest whole number of trips in the month that would flag Park under the trips condition?
- A.480
- B.720
- C.721
- D.750
- E.1,080
Show the answer
Answer: C. 721
Working
The condition is an average of more than trips a day, so more than trips in the month. The smallest whole number above 720 is 721, an average of about a day.
Why the other options are wrong
- A. This is 1 times the docks over 30 days; it leaves out the factor 1.5.
- B. 720 trips is an average of exactly 24 a day, equal to 1.5 times the docks; the rule needs more than that.
- D. This assumes the daily average must be a whole number, 25. A monthly total of 721 already gives an average just above 24.
- E. This applies the factor 1.5 twice: , where 24 is already 1.5 times the docks.
What carries over
"More than" a boundary means the next whole number past it, not the boundary itself.
Key points
Map each source in a few words: what it is, what it defines, what data it gives.
Rules usually sit in the text and numbers in the table; apply the rule row by row as a checklist.
Read "at most", "more than", "and" and "or" exactly; a row can sit exactly on the boundary.
Check whether a later source changes the situation the question asks about.
If a needed figure is in no source and cannot be built, it cannot be determined.
All questions here are original and written for UniExamer; none comes from the test maker.
Written by the UniExamer team with AI assistance. Every worked example and check question was re-solved by an independent checker before publication. No subject expert has reviewed this lesson yet. If you find a mistake, write to support@uniexamer.com.