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All questions of Square Roots and Cube Roots for GMAT Exam

How many natural numbers lie between 92 and 102?
a) 36
b) 27
c) 9
d) 18
Correct answer is option 'D'. Can you explain this answer?

Sohini Das answered
Between 92 and 102
Here, n = 9 and n + 1 = 10
∴ Natural number between 92 and 102 are (2 × n) or 2 x 9, i.e. 18.

Which of the following is a perfect square number?
  • a)
    222222
  • b)
    23453
  • c)
    1681
  • d)
    1057
Correct answer is option 'C'. Can you explain this answer?

Shashwat Singh answered
The answer is 1681 because it is the only number which has it's last digit as a number which a perfect square can have . 9×9=81 the last digit is 1.

Find the perfect square number between 30 and 40.
  • a)
    36
  • b)
    49
  • c)
    25
  • d)
    none of these
Correct answer is option 'A'. Can you explain this answer?

Amita Verma answered
Since, 1 x 1 = 1
         2 x 2 = 4
         3 x 3 = 9
         4 x 4 = 16
         5 x 5 = 25
         6 x 6 = 36
         7 x 7 = 49
 
Thus, 36 is a perfact square number between 30 and 40.

Which of the following would end with digit 1?
  • a)
    1232
  • b)
    1612
  • c)
    772
  • d)
    822
Correct answer is 'B'. Can you explain this answer?

Sneha Singh answered
Option B is correct because the unit digit of 161 is 1 and if unit digit of any digit ends with 1 the its square will also end with 1.

Without doing any calculation, find the numbers which are surely perfect squares.
  • a)
    441
  • b)
    408
  • c)
    153
  • d)
    257
Correct answer is option 'A'. Can you explain this answer?

The perfect squares have 0,1,2,4,5,6 or 9 at their units place.
Therefore153,257 and 408 are surely not perfect squares.

Without adding, find the sum. 1 + 3 + 5 + 7 + 9
  • a)
    16
  • b)
    36
  • c)
    9
  • d)
    25
Correct answer is option 'D'. Can you explain this answer?

Here, we have to find the sum of first five odd natural numbers.
Therefore, 1 + 3 + 5 + 7 + 9 = (5)2 = 25

Ones place digit in the cube of 5832 is ______.
  • a)
    5
  • b)
    7
  • c)
    2
  • d)
    8
Correct answer is option 'D'. Can you explain this answer?

A number ending with 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 0 then it's cube ends with 1 , 8 , 7 , 4 , 5 , 6 , 3 , 2 , 0 respectively  
⇒ One's digit of 5832= 2
⇒ Cube of 2=23 = 8 
So, the one's digit of cube of 5832=8

A natural number is said to be a perfect cube, if it is the cube of some ________.
  • a)
    cube number
  • b)
    square numbers
  • c)
    natural number
  • d)
    none of these
Correct answer is 'C'. Can you explain this answer?

Kavya Saxena answered
A natural number is said to be a perfect cube if it is the cube of some natural number.
Example
8 = 2 x 2 x 2
8 = 2 3
8 is the perfect cube because it is a cube of 2 which is a natural number.
But 12 is not a perfect cube because it is not a cube of any natural numbers.

Practice Quiz or MCQ (Multiple Choice Questions) with solutions are available for Practice, which would help you prepare for chapter Squares and Square Roots, Class 8, Mathematics . You can practice these practice quizzes as per your speed and improvise the topic.
Q.
Which of the following is a perfect square number?
  • a)
    222222
  • b)
    23453
  • c)
    1681
  • d)
    1057
Correct answer is 'C'. Can you explain this answer?

Sanjana Bose answered
A number is a perfect square (or a square number) if its square root is an integer; that is to say, it is the product of an integer with itself. Here, the square root of 1681 is 41.

Therefore, the square root of 1681 is an integer, and as a consequence 1681 is a perfect square.

As a consequence, 41 is the square root of 1681.

2025 plants are to be planted in a garden in such a way that each row contains as many plants as the number of rows. Find the number of plants in each row.
  • a)
    55
  • b)
    65
  • c)
    45
  • d)
    none of these
Correct answer is option 'C'. Can you explain this answer?

Rajeev Kumar answered
Let the number of rows be x
Thus, the each row contains x plants.
The total number of plants in the garden = number of rows × number of plants in each rows
Thus,
   2025=x×x
=>x=2025
=>x=  3×3×3×3×5×5
​       =3×3×5
        =45
Thus, there are 45 rows and each row contains 45 plants.

How many numbers lie between square of 12 and 13
  • a)
    22
  • b)
    23
  • c)
    24
  • d)
    25
Correct answer is option 'C'. Can you explain this answer?

Rhea Reddy answered
122 = 12*12 = 144
132 = 13*13 = 169
Now numbers are between144 and 169 are:
145, 146, 147,.............168
Total number = 24
So total numbers lies between 144 and 169 is 24

729 is the value of  _______________.
  • a)
    83
  • b)
    93
  • c)
    63
  • d)
    43
Correct answer is option 'B'. Can you explain this answer?

Rhea Kaur answered
To determine the value of 729, we need to examine the options given in the question and choose the correct one.

Let's analyze each option:

a) 83: This option does not seem to be related to the number 729. The digits in 729 do not match the digits in 83.

b) 93: This option also does not seem to be related to the number 729. Again, the digits in 729 do not match the digits in 93.

c) 63: This option does not seem to be related to the number 729 either. The digits in 729 do not match the digits in 63.

d) 43: This option does not seem to be related to the number 729. Once again, the digits in 729 do not match the digits in 43.

Therefore, none of the options provided correspond to the value of 729. As a result, the correct answer is not given in the options provided.

In conclusion, the given options are incorrect, and there is no correct answer provided for the value of 729.

What will be the unit digit of ∛216
  • a)
    3
  • b)
    6
  • c)
    4  
  • d)
    2
Correct answer is option 'B'. Can you explain this answer?

We can find it by Prime Factorization method 
³√216 = 2×2×2×3×3×3 
= 2 and 3 are making triplets i.e. 2 and 3 
= 2×3 = 6 Thus, we can say that 6 i.e option 'B' is correct.

None of the square numbers end with _________ at unit’s place.
  • a)
    3
  • b)
    2
  • c)
    7
  • d)
    2, 3, 7 or 8
Correct answer is option 'D'. Can you explain this answer?

Preeti Khanna answered
According to the Property 1, A number having 2, 3, 7 or 8 at it's unit's place is never a perfect square. In other words, no square number ebds in 2, 3, 7 or 8. 

Which of the following is a perfect cube ?
  • a)
    125
  • b)
    135
  • c)
    145                
  • d)
    115
Correct answer is option 'A'. Can you explain this answer?

Athul Sen answered
Identifying a Perfect Cube

A perfect cube is a number that can be expressed as the product of three identical factors. For example, 27 is a perfect cube because it can be expressed as 3 x 3 x 3. To determine whether a number is a perfect cube, we need to find the cube root of that number. Here, we are given four options, and we can use the cube root method to identify the perfect cube.

Solution

a) 125

The cube root of 125 is 5. Since 125 can be expressed as 5 x 5 x 5, it is a perfect cube. Therefore, option A is the correct answer.

b) 135

The cube root of 135 is approximately 5.5. Since 5.5 is not a whole number, 135 is not a perfect cube.

c) 145

The cube root of 145 is approximately 5.7. Since 5.7 is not a whole number, 145 is not a perfect cube.

d) 115

The cube root of 115 is approximately 4.8. Since 4.8 is not a whole number, 115 is not a perfect cube.

Therefore, the only perfect cube among the given options is 125, which is option A.

The cube of an odd number is always __________.
  • a)
    odd number        
  • b)
    even number
  • c)
    prime number      
  • d)
    none of these
Correct answer is option 'A'. Can you explain this answer?

Isha Desai answered
The cube of a natural odd number is always odd.
For natural numbers, we know,
odd x odd = odd
odd x even = even
even x even = even.
So, cube of a natural odd number is
odd x odd x odd
= odd x odd
= odd.
Eg.: Cube of an odd number 3 is 27, which is also odd.

The number of digits in the cube root of a 6-digit number is _______ .
  • a)
    3
  • b)
    2
  • c)
    4  
  • d)
    6
Correct answer is option 'B'. Can you explain this answer?

Jaideep Nair answered
As 100= 1000000 which is the smallest 3 digit number. So it’s only 2 digit number which is the cube root of a 6 digit number

What will be the unit digit of the cube root of a number ends with 2?
  • a)
    2
  • b)
    8
  • c)
    4
  • d)
    6
Correct answer is option 'B'. Can you explain this answer?

Because it's given cube root it will go like this
³√2 = √2
to make it a perfect square we will multiply this 2 by 2 2's again 2 x 2 x 2 = 8

so, option b) 8 is correct

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