QUANT CONCEPTS + QUIZ #12

SQUARE ROOT

Square root of any number greater than or equal to 1 but less than 100 consists of only 1 digit.

Square root of any number greater than or equal to hundred but less than 10000 consists of 2 digits.

Procedure for finding square root of perfect squares

1.     First find the last digit of the square root, which can directly be obtained by looking the last digit of the given number and then referring to the table below:

Last digit of square root	0	1	2	3	4	5	6	7	8	9
Possible last digit number	0	1,9	-	-	2, 8	5	4,6	-	-	3,7

2.    Now consider all the digits to the left of the tens digit and look at the number which remain. Think of a number whose square is just equal or less than this remaining number.

E.g.:  4096

From the above table, we get the last digit of the square root as either 4 or 6

Then we ignore 96 and focus on 40. 40 are just a little more than the square of 6. Thus 6 becomes the tens digit of our final answer.

Hence the square root is 64 and not 66 (since 4096 is more close to 60 square i.e. 3600 than to 70 square i.e. 4900).

Procedure for finding the square root of any number

E.g.: find the approximate square root value of 12345

Ignore the last two digits (units digit and the tens digit). Now consider the remaining number- 123

Since 123 lies between the squares of 11 and 12, more towards the square of 11 i.e. 121; we can estimate that the square root of 12345 will be near 110.

Now check all the options and choose the nearest answer.

Now try to solve these 10 questions as fast as possible (3-5 min)
Directions (1-5): find the square root (exact value) of the following numbers

1.    4761

          (a)  59                                (b) 69

          (c) 61                                (d) 71

2.    7569

          (a)  77                                (b) 89 

          (c) 87                                (d) 93  

3.    1849

         (a)  43                                 (b) 47  

         (c) 39                                 (d) 49

4.    3969

        (a)  61                                  (b) 63

        (c) 69                                  (d) 71

5.    9604.

        (a)  98                                  (b) 97 

        (c) 92                                  (d) 94

Directions (5-10): find the square root (approximate value) of the following numbers

6.    5555

           (a)  71                                (b) 75

           (c) 79                                (d) 69

7.    2489

           (a)  45                                (b) 53 

           (c) 50                                (d) 41

8.    13578

           (a)  111                              (b) 116 

           (c) 119                              (d) 121

9.    6879.

     (a)  80                               (b) 83

     (c) 77                                (d) 85

10.  12152

           (a)  115                             (b) 100

           (c) 105                             (d) 110

SOLUTIONS

Q	Ans	Q	Ans
1	b	6	b
2	c	7	c
3	a	8	b
4	b	9	b
5	a	10	d

Time taken

Within 3 min: EXCELLENT

3-5 min: YOU CAN DO BETTER

More than 5 min: YOU NEED TO WORK HARD