Given that −5 ≤ a ≤ 15 and 4 ≤ b ≤ 9, which of the following represents the possible values of ab?

Correct answer marked below

−45 ≤ ab ≤ 135

Correct

−45 ≤ ab ≤ −20

−20 ≤ ab ≤ 45

−20 ≤ ab ≤ 135

45 ≤ ab ≤ 135

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Explanation

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Official Explanation

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We have the ranges −5 ≤ a ≤ 15 and 4 ≤ b ≤ 9. To find the possible values of ab, we multiply the extreme values: -5 * 4 = -20,…

Comments

ANUBHANov 22, 2024

greatt question!

SJun 19, 2024

thanks!

KyathariJun 8

thanks, this one was pretty straightforward once I saw both a and b can be positive or negative

SidhantJun 11

wait, b can be negative? the range says 4 to 9 so b is always positive right?

UtkarshAug 22

got A but I almost picked D because I forgot a could be negative... glad I caught that

DevanshSep 1

same here, the negative a part is the whole trick

What this question tests

Your ability to solve and combine linear inequalities and reason about ranges of values.

Failing to flip the inequality sign when multiplying or dividing by a negative, or missing an inclusive/exclusive endpoint.