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Subject Test Math 1

Question 4 of 32

A number $n$ is increased by $8$ . If the cube root of that result equals $- 0.5$ , what is the
value of $n invisible times ?$

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$negative 15.625$

Correct Answer:

No

$negative 8.794$

Correct Answer:

No

$negative 8.125$

Correct Answer:

Yes

$negative 7.875$

Correct Answer:

No

$421.875$

Correct Answer:

No

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The correct answer is C.

One way to determine the value of $n$ is to create and solve an algebraic equation. The phrase “a number $n$ is increased by $8$ ” is represented by the expression $n + 8$ , and the cube root of that result is equal to $- 0.5$ , so $\sqrt[3]{n + 8} = - 0.5$ . Solving for $n$ gives $n + 8 = (- 0.5)^{3} = - 0.125$ , and so $n = - 0.125 - 8 = - 8.125$ .

Alternatively, one can invert the operations that were done to $n$ . Apply the inverse of each operation, in the reverse order: First cube $- 0.5$ to get $- 0.125$ , and then decrease this value by $8$ to find that $n = - 0.125 - 8 = - 8.125$ .

Question Difficulty:

easy

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Subject Test Math 1

Question 4 of 32

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