DECIMAL FRACTIONS

  • 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
  • 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.
  • Annexing zeros : to the extreme right of a decimal fraction does not change its value. Thus, 0.8 = 0.80 = 0.800, etc.
  • If numerator and denominator : of a fraction contain the same number of decimal places, then we remove the decimal sign. Thus, 1.84/2.99 = 184/299 = 8/13; 0.365/0.584 = 365/584 = 5
  • 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.
  • 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. Thus, 5.9632 x 100 = 596,32; 0.073 x 10000 = 0.0730 x 10000 = 730.
  • 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. 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
  • 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. 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.
  • 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) = 0.006
  • 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.
  • Pure Recurring Decimal : A decimal fraction in which all the figures after the decimal point are repeated, is called a pure recurring decimal.

 

Convert a Pure Recurring Decimal into Vulgar Fraction

 

  • Remove the number left to the decimal point, if any.
  • Write the repeated figures only once in the numerator without the decimal point
  • Write as many nines in the denominator as the number of repeating figures.
  • Add the number removed in step 1(if any) with the fraction obtained in the above steps.

 

 

1.0.3¯=39=13

2.0.7¯=79

3.0.36¯¯¯¯¯=3699=411

4.0.067¯¯¯¯¯¯¯¯=067999=67999

5.1.3¯¯¯=1+39=1+13=43

6.5.36¯¯¯¯¯=5+3699=5+411=5911

Convert a Mixed Recurring Decimal into Vulgar Fraction

 

  • Remove the number left to the decimal point, if any.
  • Numerator is the difference between the number formed by all the digits (taking repeated digits only once) and that formed by the digits which are not repeated
  • Denominator is the number formed by taking as many nines as the number of repeating figures followed by as many zeros as the number of non-repeating digits.
  • Add the number removed in step 1(if any) with the fraction obtained in the above steps.

 

 

1.0.5429¯¯¯¯¯=(5429−54)9900 =53759900=215396

2.0.16¯=(16−1)90 =1590=16

3.0.583¯¯¯=(583−58)900 =525900=2136=712

4.1.318¯¯¯¯¯=1+(318−3)990 =1+315990=1+63198 =1+2166=1+722=2922

Solved Question Papers

Q. Convert the following into vulgar fraction :0.75

  • 75/100
  • 1/3
  • 2/3
  • 3/4

Q. Convert the following into vulgar fraction: 3.004

  • 3004/1000
  • 304/100
  • 751/250
  • 752/251

Q. Convert the following into vulgar fraction: 0.0056

  • 8/1250
  • 7/1050
  • 7/1250
  • 7/1150

Q. Arrange the fractions 5/8, 7/12, 13/16, 16/29 and 3/4 in ascending order of magnitude

  • 7/12 < 16/29 < 5/8 < 3/4 < 13/16
  • 16/29 < 7/12 < 5/8 < 3/4 < 13/16
  • 16/29 < 3/4 < 5/8 < 7/12 < 13/16
  • 16/29 < 7/12 < 13/16 < 3/4 < 5/8

Q. arrange the fractions 3/5, 4/7, 8/9, and 9/11 in their descending order.

  • 8/9 > 13/16 > 3/4 > 9/11
  • 9/11 > 8/9 > 3/4 > 13/16
  • 8/9 > 9/11 > 3/4 > 13/16
  • 8/9 > 13/16 > 3/4 > 9/11
 

Section II : Numeric Puzzles

  • Real numbers are of two types: Decimal and Integers. The Integers have no decimal values like 0.33, 0.45; Decimals can be 0.23, 0.333… etc
  • Integers are of three types negative numbers like -1, -2 .. , zero and positive numbers like 1, 2, 3…
  • The negative numbers and zero are called non positive and zero and positive numbers are called non negative numbers.
  • Decimal numbers are of finite or terminating decimal types or infinite decimal types. The infinite decimal type is classified as rational numbers if they can be expressed in the form p / q or irrational number if they can’t be expressed in the form p / q.

Q. A number is as much greater than 36 as is less than 86. Find the number.

 

  • 61
  • 65
  • 63
  • 62

 

Q. Find a number such that when 15 is subtracted from 7 times the number, the Result is 10 more than twice the number. (Hotel Management, 2002)

 

  • 3
  • 5
  • 9
  • 7

 

 

Q. The sum of a rational number and its reciprocal is 13/6. Find the number. (S.S.C. 2000)

 

  • 2/3 or 3/2
  • 7/3 or 3/2
  • 2/3 or 5/2
  • 5/3 or 3/2

 

Q. 50 is divided into two parts such that the sum of their reciprocals is 1/ 12.Find the two parts.

 

  • 30 and 20
  • 40 and 10
  • 30 and 25
  • 40 and 20

 

Q. If three numbers are added in pairs, the sums equal 10, 19 and 21. Find the numbers

  • 6, 4 and 15
  • 6, 8 and 15
  • 7, 4 and 15
  • 6, 4 and 12