[Maths Class Notes] on Square Root of 120 Pdf for Exam

Finding the Square Root of 120 by Average Method

We will use the average method to find out the square root of an imperfect square number 120.

Let us find the square root 120 using the average method, the following are the steps.

Step 1: Find out the two perfect square numbers which are very close to the given number on either side. For example the number ‘120’, the immediate perfect square lesser than 120 is ‘100’ and the immediate perfect square greater than 120 is ‘121’.

Step 2 : Note down the square roots of the perfect squares, here the square root of ‘100’ is ‘10’ and the square root of ‘121’ is ‘11’.

Step 3 : Square root of a given number lies between the square roots of numbers determined in step 2.Square root of ‘120’ is any number between 10 and 11.

Step 4: Divide the number whose square root is determined by any of the numbers obtained in Step 2.‘120’ can be divided either by ‘10’ or ‘11’. 

Let us divide ‘120’ by ‘10’

[frac{120}{10}] = 12

Step 5: Find the average of the quotient and divisor in Step 4.

The average of 10 and 12 is

Average = [frac{10 + 12}{2}] = 11

Step 6: Now divide 120 by step 5 answer

 [frac{120}{11}] = 10.9090

Step 7: Now, average 11 and 10.9090 by adding them together and dividing the sum  by two you get 10.954545 

Check your work by multiplying your answer by itself. If 10.9545 is multiplied by 10.9545 we get 120.001.

Therefore [sqrt{120}] = 10.9545

Finding Square Root of 120 by Factors

One of the methods to find the square root of 120 is by finding the factors of 120.

Factors of 120 are 2 x 2 x 2 x 3 x 5.

Factor tree for 120 is

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Steps to find out the square root by factors 

Step 1: find out the factors of the number here

120 = 2 x 2 x 2 x 3 x 5

Step2 : Now taking root of the factors.

[sqrt{120}] = [sqrt{2 times 2 times 2 times 3times 5}]

Step 3: taking out root means taking out the pair of common factors as a single common number outside the radical sign. Here only 2 are in pairs so taking out 2 out of the radical sign. And single 2 3 and 5 does not have pair so they remain inside the radical sign

= 2  x [sqrt{2 times 3 times 5}]

Step 4: Multiplying, we get

= 2 x[sqrt{30}]

Step 5: finding the root value 

= 2 x 5.477

Step 6 : simplify 

=10.9544

Finding Square root of 120 by long Division Method

The most precise and convenient method to find out the square root of imperfect square is by long division method. Here is the stepwise calculation by long division method.

Fun Facts

• Technically, just the “check mark” part is used in  the radical; the line across the top is called the “vinculum”.

• Square Root Day- The 4th of April 2016 is a Square Root Day, because the date looks like a square root 4/4/16

• The next after that is the 5th of May 2025 (5/5/25)

[sqrt[Happy]{text{Square root Day}}]

Solved Example

Example 1: Find the square root of 12

Solution:

Factor of 12 are 2 x 2 x 3

Taking root

= [sqrt{2 times 3 times 3}]

=  [2sqrt{3}]

= 2 x 1.7320

=3.4641

Example 2 :Find the square root of 75

Solution: 

Factor of 75 = 5 x 5 x 3

Taking the root of

= [sqrt{5 times 5 times 3}]

= [5sqrt{3}]

= 5 x 1.7320

= 8.66

Quiz Time: