Cambridge IELTS 9 · Academic · Test 3 · Passage 3
Information Theory – The Big Idea — IELTS Reading Answers
All 14 answers for Information Theory – The Big Idea, Cambridge IELTS 9 Academic Reading Test 3 Passage 3, with the passage evidence and an explanation for each.
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Information Theory – The Big Idea answer key at a glance
Questions 27–40. Tap an answer to see the evidence.
What this passage tests
This passage is tested with Matching Information (Q27–32), Note Completion (Q33–37), True / False / Not Given (Q38–40). Each section below gives the strategy for that question type, the answers, and the sentence that proves them.
Questions 27–32: Matching Information
Strategy: Scan for the idea, not the exact words. The answer is a paragraph letter, and one paragraph may be used more than once unless the instructions say otherwise.
an explanation of the factors affecting the transmission of information
“In particular, Shannon showed that noise sets a limit on the rate at which information can pass along communication channels while remaining error-free. This rate depends on the relative strengths of the signal and noise travelling down the communication channel, and on its capacity (its ‘bandwidth’)”
Paragraph D explains that the error-free rate 'depends on the relative strengths of the signal and noise... and on its capacity (bandwidth)', so it covers factors affecting transmission.
an example of how unnecessary information can be omitted
“Shannon also laid the foundations of more efficient ways of storing information, by stripping out superfluous (‘redundant’) bits from data which contributed little real information. As mobile phone text messages like ‘I CN C U’ show, it is often possible to leave out a lot of data without losing much meaning”
Paragraph F shows superfluous 'redundant' bits stripped from data, using the text message 'I CN C U' as the example of omitted information.
a reference to Shannon’s attitude to fame
“While at Bell Laboratories, Shannon developed information theory, but shunned the resulting acclaim”
Paragraph B says Shannon 'developed information theory, but shunned the resulting acclaim', which is his attitude to fame.
details of a machine capable of interpreting incomplete information
“Other codes have become part of everyday life - such as the Universal Product Code, or bar code, which uses a simple error-detecting system that ensures supermarket check-out lasers can read the price even on, say, a crumpled bag of crisps”
Paragraph E describes the bar code's error-detecting system letting supermarket lasers read prices 'even on... a crumpled bag of crisps'.
a detailed account of an incident involving information theory
“In April 2002 an event took place which demonstrated one of the many applications of information theory. The space probe, Voyager 1, launched in 1977, had sent back spectacular images of Jupiter and Saturn and then soared out of the Solar System on a one-way mission to the stars”
Paragraph A opens with the April 2002 event when Voyager 1 demonstrated an application of information theory, a detailed incident.
a reference to what Shannon initially intended to achieve in his research
“He set out with an apparently simple aim: to pin down the precise meaning of the concept of ‘information’”
Paragraph C gives Shannon's initial aim: 'to pin down the precise meaning of the concept of information'.
Questions 33–37: Note Completion
Strategy: Predict the word class from the note, find the paraphrase of the note's keyword in the passage, then copy the answer exactly within the word limit.
“The space probe, Voyager 1, launched in 1977, had sent back spectacular images of Jupiter and Saturn and then soared out of the Solar System on a one-way mission to the stars”
Voyager 1 sent back images of 'Jupiter and Saturn', so the first planet named is Jupiter.
“The space probe, Voyager 1, launched in 1977, had sent back spectacular images of Jupiter and Saturn and then soared out of the Solar System on a one-way mission to the stars”
After passing Saturn the probe 'soared out of the Solar System', the destination the note records.
“Sensors and circuits were on the brink of failing”
The failing components were 'sensors and circuits', so the gap after 'sensors and' takes 'circuits'.
“The solution was to get a message to Voyager 1 to instruct it to use spares to change the failing parts”
The message told Voyager 'to use spares to change the failing parts', the noun the note needs.
“By means of a radio dish belonging to NASA’s Deep Space Network, the message was sent out into the depths of space”
The message was sent 'by means of a radio dish' belonging to NASA's Deep Space Network.
Questions 38–40: True / False / Not Given
Strategy: Judge the whole statement against the text. FALSE contradicts the passage; NOT GIVEN means the passage never addresses that specific claim.
The concept of describing something as true or false was the starting point for Shannon in his attempts to send messages over distances.
“He set out with an apparently simple aim: to pin down the precise meaning of the concept of ‘information’. The most basic form of information, Shannon argued, is whether something is true or false - which can be captured in the binary unit, or ‘bit’, of the form 1 or 0.”
'The most basic form of information... is whether something is true or false' was Shannon's starting unit before he defined transmission. TRUE.
The amount of information that can be sent in a given time period is determined with reference to the signal strength and noise level.
“This rate depends on the relative strengths of the signal and noise travelling down the communication channel, and on its capacity (its ‘bandwidth’). The resulting limit, given in units of bits per second, is the absolute maximum rate of error-free communication given signal strength and noise level”
The rate 'depends on the relative strengths of the signal and noise', confirming that signal strength and noise level set the limit. TRUE.
Products have now been developed which can convey more information than Shannon had anticipated as possible.
“As recently as 1993, engineers made a major breakthrough by discovering so-called turbo codes - which come very close to Shannon’s ultimate limit for the maximum rate that data can be transmitted reliably, and now play a key role in the mobile videophone revolution”
Turbo codes 'come very close to Shannon's ultimate limit', so they do not exceed what he anticipated; the claim of more is false.
Learn the question types in this passage
Frequently asked questions
Where does the Information Theory – The Big Idea passage come from?
It is Passage 3 of Cambridge IELTS 9 Academic Reading Test 3, and it covers Questions 27–40.
What question types appear in Information Theory – The Big Idea?
The passage is tested with Matching Information, Note Completion, True / False / Not Given. Each type is explained on this page, alongside the answers.
Are these reading answers reliable?
Every answer is paired with the sentence that proves it, so you can check each one against the passage yourself. Use the page after a timed attempt, not instead of one.
Cambridge IELTS is published by Cambridge University Press & Assessment. Band9Prep is not affiliated with Cambridge. This page is an independent study aid: it gives the answer key, the passage evidence and an explanation so you can review an attempt you have already made.