### Ratios and proportions

Ratios and proportions is one of the most important topic in aptitude because of wide range of it's applications like ages, percentages, mixtures and allegations...

Ratio is a quantitative relation between two or more numbers which tells how many times one number is w.r.t other.

If a certain amount N is divided among A, B in a ratio a:b then

A's share is a/(a+b) * N and B's share is b/(a+b) *N

If A:B = a:b and B:C = c:d then A:C = a*c : b*d

If A:B = p:q, B:C = r:s, C:D = t:u then

A:D = A/D = (A/B) * (B/C) * (C/D)

If a quantity is increased by a/b then the new content becomes (a+b)/b

If a quantity is decreased by a/b then the new content becomes (b-a)/b

To reduce your computations, it is always recommended to remember these values in terms of percentages

1/1 = 100 %

1/2 = 50 %

1/3 = 33.33 %

Ratio is a quantitative relation between two or more numbers which tells how many times one number is w.r.t other.

If a certain amount N is divided among A, B in a ratio a:b then

A's share is a/(a+b) * N and B's share is b/(a+b) *N

If A:B = a:b and B:C = c:d then A:C = a*c : b*d

If A:B = p:q, B:C = r:s, C:D = t:u then

A:D = A/D = (A/B) * (B/C) * (C/D)

If a quantity is increased by a/b then the new content becomes (a+b)/b

If a quantity is decreased by a/b then the new content becomes (b-a)/b

To reduce your computations, it is always recommended to remember these values in terms of percentages

1/1 = 100 %

1/2 = 50 %

1/3 = 33.33 %

1/4 = 25 %

1/5 = 20 %

1/5 = 20 %

1/6 = 16.66 %

1/7 = 14.28 % 1/13 = 7.6%

1/8 = 12.25 % 1/12 = 8.33%

1/9 = 11.11 % 1/11 = 9.09%

1/10 = 10 %

Proportion is a number considered in comparative relation to a whole

when 3 numbers are given a, b, c and asked to find the fourth proportion (x) then a/b = c/x

Mean proportion of two numbers a,b is x then x^2 = a*b

If A=B*C then B, C are Inversely proportional and A,B or A,C are directly proportional

If A is kept constant, Increase in B should reflect decrease in A and vise versa

If B is kept constant, Increase in one term should reflect increase in another term.

*********************************************************************************

Sample Questions:

Question 1:

If a sum of 600 rupees is divided among A and B in a ratio 2:3 then what is the difference between their shares.

Solution:

Difference = (3/5 - 2/5 )*600 = 120

A's share = 2/5 (600) = 240

B's share = 3/5 (600) = 360 or 600-240

difference = 360-240 = 120.

Question 2:

If A:B = 5:3 and B:C = 6:7, find A:B:C

Solution:

A:B = (5 : 3)*6 B:C = (6 : 7)*3

A:B:C = 30 : 18: 21

Question 3:

If A:B = 2:3, B:C = 3:4 and C:D=8:9, find A:D

Solution:

A:D = (A/B)(B/C)(C/D)

= (2/3)(3/4)(8/9)

= 4/9

Question 4:

Find the Fourth proportion (x) of 2,5,12

Solution:

2/5 = 12/x

x=6/5

Question 5:

Find the mean proportion of 625,900

Solution:

x^2 = 25^2 * 30^^2

x=25*30

x = 750

Many tricks on the way, stay tuned :)

1/7 = 14.28 % 1/13 = 7.6%

1/8 = 12.25 % 1/12 = 8.33%

1/9 = 11.11 % 1/11 = 9.09%

1/10 = 10 %

Proportion is a number considered in comparative relation to a whole

when 3 numbers are given a, b, c and asked to find the fourth proportion (x) then a/b = c/x

Mean proportion of two numbers a,b is x then x^2 = a*b

If A=B*C then B, C are Inversely proportional and A,B or A,C are directly proportional

If A is kept constant, Increase in B should reflect decrease in A and vise versa

If B is kept constant, Increase in one term should reflect increase in another term.

*********************************************************************************

Sample Questions:

Question 1:

If a sum of 600 rupees is divided among A and B in a ratio 2:3 then what is the difference between their shares.

Solution:

Difference = (3/5 - 2/5 )*600 = 120

A's share = 2/5 (600) = 240

B's share = 3/5 (600) = 360 or 600-240

difference = 360-240 = 120.

Question 2:

If A:B = 5:3 and B:C = 6:7, find A:B:C

Solution:

A:B = (5 : 3)*6 B:C = (6 : 7)*3

A:B:C = 30 : 18: 21

Question 3:

If A:B = 2:3, B:C = 3:4 and C:D=8:9, find A:D

Solution:

A:D = (A/B)(B/C)(C/D)

= (2/3)(3/4)(8/9)

= 4/9

Question 4:

Find the Fourth proportion (x) of 2,5,12

Solution:

2/5 = 12/x

x=6/5

Question 5:

Find the mean proportion of 625,900

Solution:

x^2 = 25^2 * 30^^2

x=25*30

x = 750

Many tricks on the way, stay tuned :)

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