8th Grade > Mathematics
CUBES AND CUBE ROOTS MCQs
:
B
Volume of cuboid = 3×6×9 =162 cubic units
Volume of cube = 3×3×3= 27 cubic units
Number of cubes that can be fit in the cuboid is 16227 = 6
:
D
The sum of first 5 natural numbers can be expressed as (n(n+1)2)2 where n = 5, which gives us
((5×6)2)2 =(302)2 = 152
Thus the cubes of first 5 natural numbers can be expressed as the square of 15.
:
C
Cube of 1 = 1
Cube of 2 = 8
Cube of 3 = 27
Cube of 4 = 64
So total 4 numbers have their cubes that lie between 0 and 100
:
A, B, and C
Cube root of 8 is 2 and cube root of -8 is -2. When they are multiplied together, the result is -4.
:
B
The cube of 3 = 27
The cube of 4 = 64
Since 30 lies between 27 & 64 so its cube root must lie between 3 & 4.
Hence, the given statement is false.
:
Cube of 0 is 0 (anything multiplied to 0 is 0)
:
B
8= 2 x 2 x 2
Cube root of 8 = 2
So 2+ 12 = 2.5
:
B
By prime factorization, we get 729 = 3×3×3×3×3×3=36
So cube root of 729=(729)13=363=32=9
Since, the cube root of 729 is a natural number, 729 is a perfect cube.
:
A
Take a=2 and b=1 and check.
Alternatively, we know the algebraic identity,
a3−b3=(a−b)(a2+2ab+b2)
Hence , we can see that (a−b) is a factor of a3 - b3
Thus, a3 - b3 is divisible by (a−b)
:
A
For a number to be a perfect cube, its prime factors should be in the form of triplets i.e. every prime factor should be raised to the power in multiples of 3
Prime factorizing the given number, we get 360=2×2×2×3×3×5
Hence, we can see that the given number must be multiplied by 3×5×5 i.e.75