Find the Cube Root Easily
Cube Root of a Number
Grade 6, 7,8 and Competitive Exams
First Step
Remember the cube root of the numbers from 1 to 9
Please check and remember the following points
a) Cube of number 1 is 1
b) Cube of 2 is 8 and cube of 8 ends with 2
c) So when you have to write the cube where the number ends with 2 take the number as 8 in unit place and if the number ends with 8 then take 2 in unit place
d) Cube of 3 ends with 7 and cube of 7 ends with 3
e) So when you have to write the cube where the number ends with 3 take the number as 7 in unit place and if the number ends with 7 then take 3 in unit place
f) The cubes of the remaining numbers end in the same number for example cube of 4 ends with 4, the cube of 5 ends with 5, and so on.
Lets now find the cube root of a number
110592
Step 1 : group the number
given into two parts starting from the unit place make a group of 3
numbers and let the remaining numbers be
in the other group. So in this case the two groups are 110592
Step 2: Find the number
whose cube ends with 2 which is 8 as cube of 8 is 512 – Write 8 under the unit
place.
Step 3: Find the perfect
cube that comes before 110, the number is 64 and 64 is cube of 4 so our second
number is 4 and the answer is 48
Lets take one more example
10648
Grouping it by above method we
have 10648
The cube of 2 is 8 so our unit
digit number is 2
The number having a perfect cube
before 10 is again 2
Hence we have our answer as 22
Taking one more example 54872
The 2 groups are 54 and 872
The number having a cube that ends
with 2 is 8 ( cube of 8 is 512)
The number having the perfect cube
before 54 is 3 ( cube of 3 is 27 where as cube of 4 is 64 which is more than
54)
So our answer is 38
Try the following worksheet with your children