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Published on: 24/09/2019
Square and Square Roots
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1.
We check 256 is a perfect square or not.
2.
In a right angled \(\Delta\) ABC, if \(\angle\)B=90°, AB=12 cm and BC=5 cm, then find AC.
3.
Find the square root of 324 by the method of repeated subtraction.
4.
Find the least number that must be added to 1500. so as to get a perfect square. Also, find the square root of the perfect square.
5.
A ladder 10 m long rests against a vertical wall. If the foot of the ladder is 6 m away from the wall and the ladder just reaches the top of the wall, how high is the wall?
6.
Find the square roots of 100 by the method of repeated subtraction.
7.
The sum of two numbers, when multiplied with each of the numbers separately, then the result of the above multiplications are 2418 and 3666, respectively. Find the difference between the numbers.
8.
If the expression X x 809436 x 809436 be a perfect square, then find the value of x.
9.
Find the value of \(\sqrt { 248+\sqrt { 52+\sqrt { 144 } } } \)
10.
Find the square root of the following by long division method 5625
1.
Resolving 256 into prime factors, 256 = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2
Grouping the factors in pairs in such a way that both the factors in each pair are same.
256 = 22 x 22 x 22 x 22
Here, 256 can be grouped into pairs of equal factors and no factor is left over.
| 2 | 256 |
| 2 | 128 |
| 2 | 64 |
| 2 | 32 |
| 2 | 16 |
| 2 | 8 |
| 2 | 4 |
| 2 | 2 |
| 1 |
Hence, 256 is a square number.
Again, 2 X 2 x 2 X 2 = 16
50,256 is the square of 16.
2.
According to Pythagoras theorem,
(Hypotenuse)2 = (Base)2 + (Perpendicular)2
Clearly, the side opposite to 90° is hypotenuse
AC = Hypotenuse
AB = Base
BC = Perpendicular

(AC)2 = (AB)2 + (BC)2
\(\Rightarrow\) (AC)2 =(12)2 +(5)2
\(\Rightarrow\) (AC)2=144+25
\(\Rightarrow\) (AC)2 =169
\(\Rightarrow\) AC =\(\sqrt { 169 } \) = 13 cm
3.
Here, 324 -1 = 323,323 - 3 = 320
320 - 5 = 315,315 -7 = 308
308 - 9 = 299, 299 - 11 = 288
288 -13 = 275,275 -15 = 260
260 - 17 = 243, 243 - 19 = 224
224 - 21 = 203,203 - 23 =180
180 - 25 =155, 155 - 27 =128
128 - 29 = 99, 99 - 31 = 68
68 - 33 = 35, 35 - 35 = 0
So, to get 0, we use 18 steps.
Hence, square root of 324 is 18.
4.
We have, 1500

We see that, 382 < 1500 < 392
So, number to be added = 392 - 1500
= 1521 - 1500 = 21
Therefore, the perfect square is 1500 + 21 = 1521 and \(\sqrt { 1521 } \)= 39
So, the required number is 21 and the square root is 39.
5.
Let AC be the ladder. Therefore.
AC=10 m

Let BC be the distance between the foot of the ladder and the wall.
Therefore,BC = 6 m
\(\Delta\) ABC is a right angled triangle, right angled at B.
By using Pythagoras theorem,
AC2 = AB2 + BC2
\(\Rightarrow\) 102 = AB2 + 62
\(\Rightarrow\) AB2 =102 - 62
\(\Rightarrow\) AB2 = 100 - 36 = 64
\(\therefore\) AB = \(\sqrt { 64 } \) = 8m
Hence, the wall is 8 m high.
6.
To find the square roots of 100, we subtract successive odd number starting from 1 as follows:
100 - 1 = 99, 99 - 3 = 96, 96 - 5 = 91, 91 - 7 = 84
84 -9 = 75, 75 -11 =64, 64 -13 = 51,51-15 =36
36-17 = 19, 19 - 19 = 0
We observe that the number 10 reduced to zero after subtracting first 10 odd numbers.
So, 100 is a perfect square.
\(\therefore \ \sqrt { 100 } =10\)
Hence, the square root of 100 is 10.
7.
16
8.
1
9.
Given that, \(\sqrt { 248+\sqrt { 52+\sqrt { 144 } } } =\sqrt { 248+\sqrt { 52+12 } } \)
\(\left[ \because 144={ (12) }^{ 2 } \right] \)
\(=\sqrt { 248+\sqrt { 64 } } =\sqrt { 248+8 } [\because 64={ (8) }^{ 2 }]\)
\(=\sqrt { 256 } =16\)
Hence, value of the expression is 16.
10.

\(\therefore \ \sqrt { 5625 } =75\)
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