Page 33 - SM inner class 8.cdr

Example 30. Evaluate 2 correct up to two Example 31. Evaluate
places of decimal. 0.894
08 correct up to two
.
Solution: Using the 1.414 places of decimal. 8 0.8000 00
division method, we Solution: Using the +8 64
may find the value of 1 2.0000 00 division method, we 169 1600
2; +1 1 may find the value of +9
24 1 00 – 1521
Therefore, 2 = 1.414 08 as shown below. 7900
.
Þ 2 = 1.41 +4 – 96 1784
(correct up to 2 places 281 400 Therefore, +4 7136
.
of decimal) 08 = 0.894 764
+1 281
.
Þ 08 = 0.89
2824 11900 (correct up to 2 places of decimal)
+4 11296
601

E xercise 3.4

1. Eval u ate the square root of the follow ing numbers in deci mal form:
(i) 169 (ii) 3364. (iii) 1369. (iv) 7569
.
.
.
.
(v) 177241 (vi) 4225. (vii) 10816. (viii) 813604
2. Eval u ate 3 up to two places of deci mal.
3. Eval u ate 7 correct up to two places of deci mal.

Summary

m The square of a number is that number which m Finding the square roots by prime factorisation,
raised to the power 2. division method and repeated subtraction.
m A rational number that is equal to the square of m Square root is the inverse operation of squaring.
another rational number is called perfect square. m Estimating square roots of non perfect square
m Estimating number of digits in square of a number. numbers.
m For any natural number m greater than 1,
2
2
(2m ,m - 1 )(m + is a Pythagorean triplet.
) 1
Review Exercise
1. What will be the number of zeros in the square 6. There are 500 chil dren in a school. For a P.T.
of 5000? drill they have to stand in such a manner that
2. Find the square of 39. the number of rows is equal to number of
columns. How many chil dren would be left out
3. Find the square roots of 1225.
in this arrange ment.
4. Find the perfect square numbers between 120
7. What will be the value of ‘x’ in Pythagorean
and 130.
trip let (6,8, x)?
5. The students of Class VIII of a school donated
Rs2916 in all, for Prime Minister’s National 8. Which is the greatest three-digit perfect
Relief Fund. Each student donated as many square?
rupees as the number of students in the class. 9. What is the small est square number which is
Find the number of students in the class. divis i ble by each of the numbers 6,9 and 15 ?

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Mathematics In Focus - 8