I. Decimal Fractions : Fractions in which denominators are powers of 10 are
known as decimal fractions.
Thus ,1/10=1
tenth=.1;1/100=1 hundredth =.01;
99/100=99
hundreths=.99;7/1000=7 thousandths=.007,etc
II. Conversion of a Decimal Into Vulgar
Fraction : Put 1 in the denominator under
the decimal point and annex with it as many zeros as is the number of digits
after the decimal point. Now, remove the decimal point and reduce the fraction
to its lowest terms.
Thus,
0.25=25/100=1/4;2.008=2008/1000=251/125.
III. 1. Annexing
zeros to the extreme right of a decimal fraction does not change its value
Thus, 0.8 = 0.80 = 0.800, etc.
Thus, 0.8 = 0.80 = 0.800, etc.
2. If numerator and denominator of a fraction
contain the same number of decimal
places, then we remove the decimal sign.
places, then we remove the decimal sign.
Thus, 1.84/2.99 = 184/299 = 8/13; 0.365/0.584 = 365/584=5
IV. Operations on Decimal
Fractions :
1. Addition and Subtraction of Decimal
Fractions : The
given numbers are so
placed under each other that the decimal points lie in one column. The numbers
so arranged can now be added or subtracted in the usual way.
placed under each other that the decimal points lie in one column. The numbers
so arranged can now be added or subtracted in the usual way.
2. Multiplication of a Decimal
Fraction By a Power of 10 : Shift the decimal
point to the right by as many places as is the power of 10.
point to the right by as many places as is the power of 10.
Thus, 5.9632 x 100 = 596,32; 0.073 x 10000 = 0.0730 x 10000
= 730.
3.Multiplication
of Decimal Fractions : Multiply the given numbers considering
them without the decimal point. Now, in the product, the decimal point is marked
off to obtain as many places of decimal as is the sum of the number of decimal
places in the given numbers.
them without the decimal point. Now, in the product, the decimal point is marked
off to obtain as many places of decimal as is the sum of the number of decimal
places in the given numbers.
Suppose we have to find the
product (.2 x .02 x .002). Now, 2x2x2 = 8. Sum of decimal places = (1 + 2 + 3)
= 6. .2 x .02 x .002 = .000008.
4.Dividing a
Decimal Fraction By a Counting Number : Divide the given
number without considering the decimal point, by the given counting number.
Now, in the quotient, put the decimal point to give as many places of decimal as
there are in the dividend.
number without considering the decimal point, by the given counting number.
Now, in the quotient, put the decimal point to give as many places of decimal as
there are in the dividend.
Suppose we have to find the
quotient (0.0204 + 17). Now, 204 ^ 17 = 12. Dividend contains 4 places of
decimal. So, 0.0204 + 17 = 0.0012.
5. Dividing a Decimal Fraction By a Decimal
Fraction : Multiply both the dividend and the divisor by a suitable power
of 10 to make divisor a whole number. Now, proceed as above.
Thus,
0.00066/0.11 = (0.00066*100)/(0.11*100) = (0.066/11) = 0.006V
V. Comparison of Fractions : Suppose some fractions are to be arranged in ascending or
descending order of magnitude. Then, convert each one of the given fractions in
the decimal form, and arrange them accordingly.
Suppose, we have to arrange the
fractions 3/5, 6/7 and 7/9 in descending order.
now, 3/5=0.6,6/7 = 0.857,7/9 =
0.777....
since 0.857>0.777...>0.6, so 6/7>7/9>3/5
VI. Recurring Decimal : If in a decimal fraction, a figure or a set of figures is
repeated continuously, then such a number is called a recurring decimal.
In a recurring decimal, if a single figure is repeated,
then it is expressed by putting a dot on it. If a set of figures is repeated,
it is expressed by putting a bar on the set
Thus 1/3 = 0.3333….= 0.3;
22 /7 = 3.142857142857.....= 3.142857
No comments:
Post a Comment