10) Estimate the cube roots of the following
a) 91129
b) 551368 c) 4913
Answers
Step-by-step explanation:
Solution:-
For calculating the cube root of 4913, this number has to be separated in to groups starting from the rightmost digit
The groups are 4 and 913.
Considering the group 913
913 ends with 3 and we know that if the digit 3 is at the end of any perfect cube number, then its cube root will have 7 at its units place only. Therefore the digit at the units place of the required cube root is taken as 7.
Now considering the other group 4
We know that 1³ = 1 and 2³ = 8
Also, 1 < 4 < 8
So, 1 will be taken at the tens place. so the required cube root of 4913 is 17.
∛4913 = 17
Answer.
Cube root of 12167
We shall separate 12167 in to groups.
The groups are 12 and 167
167 ends with 7 and we know that if 7 is at the units place of any perfect cube number then its cube root will have 3 at its units place only. therefore, the digit at the units place of the required cube root is taken as 3.
Now considering the other group 12.
2³ = 8 and 3³ = 27
And also 8 < 12 < 27
2 is smaller than 3, therefore 2 will be taken as the digit at tens place of the required cube root.
Thus,
∛12167 = 23
Answer.
Cube root of 32768
We shall separate 32768 in to groups.
The groups are 32 and 768.
768 ends with 8. We know that if the digit 8 at the units place of perfect cube number, then its cube root will have 2 at its units place only. So, the digit at the units place of the required cube root is taken as 2.
Now, considering the other group 32.
3³ = 27 and 4³ = 64
Ans also, 3 < 32 < 64
3 is smaller than 4, so 3 will be taken as the digit at the tens place of the required cube root.
∛32768 32
Answer.
Answer:
a) = 90000+1000+100+20+9
b) = 500000+50000+1000+300+60+8
c) =4000+900+10+3