Ratio and Proportion - Examples (with Solutions), Algebra, Quantitative Aptitude Quant Notes | EduRev

Concept
If a and b (b ≠ 0) are two quantities of the same kind, then Ratio is the relation which one quantity bears to
another of the same kind in magnitude.

Now in two quantities a and b the fraction   is called the ratio of a to b. It is usually expressed as a : b, a and
b are said to be the terms of the ratio. The former (numerator) ‘a’ is called the Antecedent of the ratio and
latter (denominator) ‘b’ is called consequent.

Basics of Ratio
(i) As ratio is a relation between two quantities so ratio is independent of the concrete units employed in
the quantities compared.
(ii) Ratio exists only between two quantities; both the quantities must be in the same units.

Composition of Ratio
 

I. Compounded Ratio
When two or more ratios are multiplied term wise, the ratio thus, obtained is called their compounded
ratio.
Compounded ratio of (a : b, c : d and e : f) 

II. Reciprocal Ratio
For any ratio a : b, the reciprocal ratio will be 

The application of it is in calculating the ratio of the wages distributed among the workers, which is
equal to the reciprocal ratio of number of days taken by them to complete the work.

Proportion
When two ratios are equal, the four terms involved, taken in order are called proportional, and they are said to
be in proportion.
1. The ratio of a to b is equal to the ratio of c to d i.e. if   , we write a : b : : c : d

2. If a : b : : c : d Then we have ad = bc
i.e. the terms a and d are called Extremes and, the terms b and c are called the Means. The term a, b, c
and d are known by the name 1st, 2nd, 3rd and the 4th proportion respectively.

Continued Proportion:
Three quantities are said to be in continued proportion, if the ratio of the first to the second is same as the
ratio of the second to the third.
Thus a, b and c are in continued proportion if a : b = b : c

Mean Proportion:
If a, b, c are in continued proportion then second quantity ‘b’ is called the mean proportional between ‘a’ and
‘c’ and a, b and c are known as 1^st, 2^nd and 3^rd proportion respectively.

Ratio & Proportion

Ex.1 What is the mean proportional to 
 

(1) 

(2) 

(3) 

(4) 

Sol.

Ex.2 What should be added to each of the numbers 19, 26, 37, 50 so that the resulting number should
 be in proportion?
 (1) 2 

(2) 3 

(3) - 2 

(4) - 5

Sol. Let the required number be x.

Basics of Proportion
(i) Let us take four quantities a, b, c & d such that they are in proportion i.e. a : b : : c : d then,

This operation is called componendo and Dividendo.

(ii) If  = then

Partnership & Share

Ex.3 Saman begins business with a capital of Rs. 50,000 and after 3 months takes Manu into
 partnership with a capital of Rs. 75000. Three months later Amandeep joins the firm with a
 capital of Rs. 1, 25,000. At the end of the year the firm makes a profit of Rs. 99,495. How much of
 this sum should Amandeep receive?
 

Sol. Money invested by Saman for 12 months = Rs. 50,000
Money invested by Manu for 9 months = Rs. 75000
Money invested by Amandeep for 6 months = Rs. 1,25,000
Share of Saman: Manu: Amandeep
= 50,000 × 12 : 75,000 × 9 ; 1,25,000 × 6
= 6,00,000 : 6,75,000 : 7,50,000 = 600 : 675 : 750 = 8 : 9 : 10
Total profit = Rs. 99,495.
Profit of Amandeep =

PROPORTIONS

Direct Proportion
If A is directly proportional to B, then as A increases B also increases proportionally or in other words the
proportional change occurs in the same direction. In general when A is directly proportional to B, then

Examples of Direct proportion are Time & Distance problems; time taken to
travel a distance is directly proportional to the distance traveled when the
speed is constant. This means the distance-traveled doubles if the time taken
doubles provided speed remains constant.

Direct Relation
In these types of cases an increase in one causes increase in the other but the
increase is not proportional as in the case of direct proportion.

For example:
With simple interest the amount increases with increase of the number of years
but not proportionally while on the other hand interest doubles or triples after 2nd
and 3rd years. So the increment in amount is in direct relation while increment in interest is direct proportion.

Ex.4 If 6 men can lay 8 bricks in one day, then how many men are required to lay 60 bricks in the
 same time?
 (1) 45 men 

(2) 40 men 

(3) 60 men 

(4) 50 men

Sol. Since the time is same so to do more work we need more persons. Hence this is the problem of direct
proportion,



Ex.5 The cost of New Year party organized in TCY is directly related to the number of persons
 attending that party. If 10 persons attend the party the cost per head is Rs 250 and if 15 people
 attend, the cost per head is Rs. 200. What will be the total cost of the party if 20 persons attend
 it?

Sol. This is the problem of direct relation
Let the total cost of party is

Indirect/Inverse Proportion

A is in indirect proportion to B if as A increases, B decreases
proportionally i.e. the proportional change occurs in the opposite direction.
In general if A is in indirect proportion to B, then
AB = constant.
Examples of Indirect proportion are Price & Quantity (expenditure
remaining same), Number of men required & rate of work done (amount
of work remaining same), Time & Speed problems for same distance.

Ex.6 If 6 men can build a wall in 9 days then 60 men can build a similar wall in ______ days?

Sol. Work = Men x Days

Ex.7 A can do a piece of work in 12 days, B is 60% more efficient than A. Find the number of days
 required for B to do the same piece of work.

Sol. Ratio of the efficiencies is A : B = 100 : 160 = 5 : 8. Since efficiency is inversely proportional to the
number of days, the ratio of days taken to complete the job is 8 : 5

Ex.8 Ten years ago, the ratio of ages of A and B is 3 : 4, now, it is 4 : 5. What is the present age of A?
 

Sol. 10 years ago, let their ages be 3k and 4k.
So, present ages are 3k + 10 and 4k + 10.
The ratio is given as 4 : 5.


Ex.9 Three friends A, B, C earn Rs. 2000 together. If they want to distribute this money such that ‘A’
 should get Rs. 300 more than B and Rs. 100 more than C, in what ratio, they have to distribute
 the money?

Sol. A = 300 + B = 100 + C
So, A = 300 + B and C = 200 + B
A + B + C = 2000
∴ B = 500 ⇒ A = 800 and C = 700 So, the required ratio = 8 : 5 : 7

Ex.10 Four friends A, B, C, D share Rs. 10,500 in the ratio  how much more money A
 and C together get than B and D together?

Sol. The given ratio is

Multiply with 24 = 8 : 6 : 4 : 3.
Take A = 8k, B = 6k, C = 4k, D = 3k.
Total = 21k = 10,500
⇒ k = 500
Required answer = (A + C) - (B + D)
= (8k + 4k) - (6k + 3k) = 3k = Rs. 1500