The cube root of $.000216$ is
Aptitude
Square Root and Cube Root
Difficulty: Easy
Choose an option
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A.6
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B.06
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C.006
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DNone of these
Answer
Correct Answer: .06
Explanation
Concept & Strategy
When finding the cube root of a decimal, first find the cube root of the non-zero integer part. Then, count the total number of decimal places in the original number. The final cube root will have exactly one-third the number of decimal places as the original perfect cube.
Step-by-Step Solution
* **Given number**: $0.000216$
* Count the decimal places: There are $6$ digits after the decimal point.
* Find the cube root of the integer part. The significant integer part is $216$. We know from standard cubes that:
$$6^3 = 216$$
* So, $\sqrt[3]{216} = 6$.
* Determine correct decimal placement: Divide the number of original decimal places ($6$) by $3$ (since it is a cube root).
$$6 \div 3 = 2$$
* The final cube root must have exactly $2$ decimal places. Applying this format to our integer root $6$ gives $0.06$.
Exam Strategy & Shortcut
Recognize $216$ as $6^3$ instantly. See the $6$ decimal places in the question. Apply the rule: the root must have $6/3 = 2$ decimal places. Immediately select $.06$ from the options without writing anything down.
Common Pitfall
Placing the decimal point incorrectly is the most common error. Students often select $.006$ by just visually carrying over zeros, or $.6$ by incorrectly confusing the decimal reduction rules of cube roots with square roots.
Final Answer
**Therefore, the correct answer is .06.**