Cube Root Using Digits


 
 
Concept Explanation
 

Cube Root Using Digits

Cube roots of perfect cubes up to 6 digits can be easily found by this method. From the table of cubes, we observe that the cube of a number ending in 0,1,2,3,4,5,6,7,8, and 9 ends in 0,1,8,7,4,5,6,3,2, and 9, respectively .Thus, by looking at the ones digit of a perfect cube, we can determine the ones digit of its cube root. To determine the other digits of the cube root, we follow the following steps:

Step 1: look at the digit at the ones place of the perfect cube and determine the digit at the ones place in the cube root of the given number.

Step 2: Strike out from the right, the last three digits of the number. If nothing is left, we stop. The digit in step 1 is the cube root of the given number.

Step 3: Now consider the leftover number from step 2. Find the largest 1-digit number whose cube is less than or equal to this leftover number. This is the tens digit of the cube root of the given number.

Illustration: Find the cube root of 512 by using its ones and tens digits.

Solution: The ones digits of the number 512 is 2.

Hence, the digit at the ones place in the cube root of 512 is 8.No number is left after striking out the three digits from the right (ones, tens, and hundreds) of the number.

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Sample Questions
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Question : 1

Find the tens digit in the cube root of 2197.

Right Option : A
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Question : 2

Find the tens digit in the cube root of 185193.

Right Option : A
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Explanation
Question : 3

Find the tens digit in the cube root of 636056.

Right Option : B
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Explanation
 
 
 


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