Page 50 - ICSE Math 8

Example 20: Evaluate: 169 × 225

Solution: 169 × 225 = 169×225 ( x × y = xy )

= 13×13×3×3×5×5 = 13 × 3 × 5 = 195

EXERCISE 3.5

1. Find the square root of the following.

256 7,225 2,209 17 120
(a) (b) (c) (d) 26 (e) 1
841 1,089 324 64 169
2. Evaluate the following.

(a) 512 × 1,250 (b) 243× 14,700 (c) 625 × 81 (d) 16,807 × 6,300
193
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3. Ravi walks around a square field of area 2 m. Find the distance covered by Ravi in 2 rounds of the field.
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4. The area of a square is equal to the area of a rectangle whose dimensions are 48 cm and 27 cm. Find the
side of the square.
5. Concrete mix is being used to lay tiles in a rectangular plot of length 45 m and breadth 20 m. Exactly
the same amount of concrete is required to lay floor tiles in a square plot. What is the length of the side
of the square plot?
Square Roots of Rational Numbers in Decimal Form
To find the square root of a rational number in the decimal form, follow the given steps.
Step 1: Prepare the number.
(a) In the given number, bars should be placed forming pairs starting from far right side in the integral
part of the number.
(b) However, bars should be placed forming pairs starting from far left side in the decimal part of
the given number.
Example: 12345 6789◊
 

Add zeros, if required in the decimal part of the given number to complete the pairs.

Step 2: Repeat rest of the steps to find the square root. Place the decimal point in the square root immediately
when the integral part is exhausted.

Example 21: Find the square root of 27.04. Example 22: Find the square root of 90.25.

Solution: Solution:
5.2 9.5
5 27.04 9 90.25
25 81
102 2 04 185 925
2 04 925

0 0

\ 27.04 = 5.2 \ 90.25 = 9.5

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