• All About Ratio And Proportion

    What is Ratio?

    A ratio is a relationship between two numbers by division of the same kind. The ration of a to b is written as a : b = a / b In ratio a : b , we can say that a as the first term or antecedent and b, the second term or consequent.

    Example : The ratio 4 : 9 we can represent as 4 / 9 after this 4 is a antecedent and , consequent = 9

    Rule of ration : In ratio multiplication or division of each and every term of a ratio by the same non- zero number does not affect the ratio.

    What is Proportion?

    The idea of proportions is that two ratio are equal.

    If a : b = c : d, we write a : b : : c : d,

    Ex. 3 / 15 = 1 / 5

    a and d called extremes, where as b and c called mean terms.

    Proportion of quantities

    the four quantities a, b, c, d said proportion then we can express it a : b = c : d

    Then a : b : : c : d <–> ( a x d ) = ( b x c ) product of means = product of extremes.

    If there is given three quantities like a, b, c of same kind then then we can say it proportion of continued.

    a : b = b : c the middle number b is called mean proportion. a and c are called extreme numbers.

    So, b2 = ac. ( middle number )2 = ( First number x Last number ).

    Quiz on ratio and proportion:-

    1 If P : Q : R = 2 : 3 : 4 , Then P / Q : Q / R : R / P = ?

    A. 8: 9: 24     B. 7: 9: 24    C. 4: 6: 15    D. 8: 11: 24    E. None of these

    2: If 2P = 3Q = 4R, Then P : Q : R = ?

    A. 2: 3: 5    B. 2: 3: 4    C. 3: 5: 6    D. 1: 2: 3    E. None of these

    3: If P : Q = 2 : 3 , Q : R = 4 : 5 and R : S = 6 : 7 , then P : S = ?

    A. 18: 25    B. 17: 35    C. 16: 35    D. 8: 11    E. None of these

    4:Rama distributes his pencil among his four friends Rakesh, Rahul, Ranjan, and Rohit in the ratio 1 / 2 : 1 / 3 : 1 / 4 : 1 / 5 . What is the minimum number of pencils that the person should have?

    A. 66    B. 64    C. 72     D. 77    E. None of these

    5: Two numbers are respectively 40% and 60% more than third number. Find the ration of two numbers ?

    A. 8: 7    B. 7: 9    C. 9: 11    D. 8: 13    E. None of these

    Answers with Explanation:-

    1. P : Q : R = 2 : 3 : 4 .

    Let P = 2k,

    Q = 3k,

    R = 4k.

    Then,

    P / Q = 2k / 3k = 2 / 3 ,

    Q / R = 3k / 4k = 3 / 4

    R / P = 4k / 2k = 2 / 1.


    2. Let 2P = 3Q = 4R = k ,

    Then ,

    P = k / 2,

    Q = k / 3 ,

    R = k / 4.

    SO , P : Q : R = k / 2 : k / 3 : k / 4 = 6 : 4 : 3.


    3. (C)


    4. Rakesh : Rahul : Ranjan : Rohit = 1 / 2 : 1 / 3 : 1 / 4 : 1 / 5

    Step 1: At First we need to do is LCM of 2,3,4 and 5 is 60.

    Step 2: Then pencil are distributed in ratio among friends,

    Rakesh = ( 1 / 2 x 60 ) = 30.

    Rahul = ( 1 / 3 x 60 ) = 20.

    Ranjan = ( 1 / 4 x 60 ) = 15.

    Rohit = ( 1 / 5 x 60 ) = 12.

    Step 3: Total number of pencils are ( 30 x + 20 x + 15 x + 12 x) = 77 x.

    For minimum number of pencils x = 1 .


    5.Step 1: Let the third number is A

    Then first number is 140% of A = 140 x A / 100 = 7A / 5 and second number is 160% of B = 160 x B / 100 = 8B /5.

    Step 2: now ratio of first and second number is 7A / 5 : 8B / 5 = 35A : 40B = 7 : 8.