Unit 12 · Multi-Step Conditional Reasoning
Pool Balls — Which Must Be True?
Lesson 7 of 16
About this lesson
Three pool balls in a line — but we only know the colours of Ball 1 and Ball 3. Ball 2's colour is a mystery. The question asks which statement MUST be true. The trick is that you can't know which statement is true in one scenario only — you need to find something that holds up no matter what colour Ball 2 turns out to be. This is the "must be true under all valid arrangements" skill.
Chapters
Question
Three balls – each of which is either red or yellow – lie in a straight line on a pool table. Aziz strikes the first ball, which is red. That ball hits the middle ball. The middle ball then hits the last ball, which is yellow.
On the basis of this information, which one of the following statements must be true?
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