Page 31 - SM inner class 7.cdr

19 So lu tion : (i) By Place Value Prin ci ple
So lu tion : (i) , the de nominator is 64 and
64 5 = 5
64 = 2 ´ 2 ´ 2 ´ 2 ´ 2 8 2 ´ 2 ´ 2
Thus, the only prime factor of 64 is 2. Since each 2 needs to be multiplied by a ' '5 to
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So, must have a terminating decimal change it into a ' '10 we have
64 5 5 5 1 5 1 5
representation. = ´ ´ ´ ´ ´
8 2 5 2 5 2 5
So, we can conclude that, 5 ´ 5 ´ 5 ´ 5
=
Note : If the de nom i na tor of a frac tion num ber in 2 ( ´ 5) ´ 2 ´ 5) ´ 2 ´ 5)
(
(
stan dard form has no prime fac tors other then 2 or
5, then it can be rep re sented as a ter mi nat ing = 625 = 625 = 0625
.
´
decimal. 10 ´10 10 1000
23 (ii) By Long division Method
(ii) In , the denominator is 48 and
48 5
48 = 2 ´ 2 ´ 2 ´ 3 =
8
Since, the prime factors of 48 are 2 and 3 0.625
23 8 5.0000
therefore does not have a terminating –48
48 20
decimal representation. –16
5 40
Ex am ple 23. Write the dec i mal form of us ing –40
8 0
(i) the place value principle and (ii) the long
di vi sion method.

E xercise 3.3

1. Con vert :
(a) 3.4 km to m (b) 1568 ml to l (c) 12.034 kg to g
(d) 2310 m to km (e) 4.7 l to ml (f) 0.87 kl to l
(g) 9876 mm to m (h) 450 m to km (i) 125 mm to m (j) 500 mg to kg

2. De ter mine which of the fol low ing ra tio nal num ber have a ter mi nat ing dec i mal rep re sen ta tion or non
ter mi nat ing decimal?
6 3 6 7 5
(a) (b) (c) (d) (e)
60 20 15 17 18
4
3. Write the dec i mal from of us ing
16
(a) the place value principle (b) the long division method.
15
4. Write the dec i mal form of us ing
25

(a) the place value principle (b) the long division method

Word Problems on Decimals Ex am ple 24. The product of two numbers is
Word problems on decimals are solved here 42.63. If one num ber is 2.1, find the other.
step by step. So lu tion : Prod uct of two num bers = 42.63

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Mathematics In Focus - 7