A box contains a certain number of balls, marked successively from 1 to n. If there are 45 different ways that two balls can be selected from the box such that the ball with number 3 marked on it is not selected, then what is the value of n?
Correct answer: A
Explanation
(n-1)C2=45
n-1=10
n=11
The answer is A.
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Source: Algebra word problems from the AQuA-RAT dataset (Ling et al., 2017), published by Google DeepMind under the Apache License 2.0.
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AQuA-RAT items are crowdsourced algebra problems, not ACT questions. They carry five answer choices in the pre-2025 ACT Mathematics style and no ACT reporting category. Useful for drilling Preparing for Higher Math content; not a substitute for a real form.