Question

State true or false with a valid reason.
(i) The cube of any odd number is even
(ii) A perfect cube does not end with two zeroes.
(iii) If a square of a number ends with 5, then its cube ends with 25.
(iv) There is no perfect cube that ends with 8.

Answer 1

(i)The cube of any odd number is even - False.
Reason:
When we find out the cube of an odd number, we will find an odd number as the result because the unit place digit of an odd number is odd and we are multiplying three odd numbers.
Therefore, the product will again be an odd number.
For example, the cube of 7 (i.e., an odd number) is 343, which is again an odd number.

(ii) A perfect cube does not end with two zeroes. - True.
Reason:
Perfect cube will end with a certain number of zeros that are always a perfect multiple of 3.
For example, the cube of 10 is 1000 and there are 3 zeroes at the end of it.
The cube of 100 is 1000000 and there are 6 zeroes at the end of it.

(iii) If a square of a number ends with 5, then its cube ends with 25-False.
It is not always necessary that if the square of a number ends with 5, then its cube will end with 25.
For example, the square of 25 is 625, and 625 has its unit digit as 5. The cube of 25 is 15625.
However, the square of 35 is 1225 and also has its unit place digit as 5 but the cube of 35 is 42875 which does not end with 25.

(iv) There is no perfect cube that ends with 8- False.
Reason:
There are many cubes that will end with 8.
The cubes of all the numbers having their unit place digit as 2 will end with 8.
The cube of 12 is 1728 and the cube of 22 is 10648.