Monday, April 30, 2012

Ratio and Propotion Excercise


1.If a:b=3:7,find the value of (5a+b):(4a+5b)
a)15:44      b)22:35 c)15:49 d)22:47

2.The ratio between two number is 3:5 and their is 40.Find the larger of two numbers
a)15  b)20    c)25    d)40

3.A bag contains one rupee,50 paise and 25 paise coins in the ratio 1:2:4.If the
total amount is Rs 75,then find the number of 50 paise coins in the bag
a)25  b)50    c)75    d)100

4.If (x+4):(3x+15) is the triplicate of 2:3.Find the value of x
a)1   b)3     c)4     d)none of these

5.If a is 75% of b,b is 150% of c and d is 25% of c,then find a:d
a)9:1 b)9:2   c)8:3   d)8:1

6.The present ages of two persons are in the ratio 7:8.Twenty years ago the ratio of their ages was 9:11.Find the present age of the older son
a)64 years   b)72 years     c)56 years     d)40 years

7.Find x:y:z,if 2x+y-5z = 0 and 3x-2y-4z=0
a)1:2:1      b)1:1:1 c)1:1:2 d)2:1:1

8.A certain sum is divided among A,B and C in a manner that for every rupee that A gets,B gets 75 paise and for every rupee that B gets,C gets 50 paisee.If B's share in the total sum is Rs 840.Find the share of A

  a)Rs 2380    b)Rs 2240      c)Rs 1750      d)Rs 1120

9.Seventy eight is divided into two parts such that five times the first part and four times the second part are in the ratio 15:14.Find the first part
  a)32  b)36    c)42    d)46

10.A certain amount of money  is divided among A,B and C such that A gets half of what B and C gets together.B gets one third of what A and C together get.If A got Rs 500 more than B,then how much money was divided?
a)Rs4500     b)Rs 6000      c)Rs 8000      d)none of these

11.In a school there are 650 students.The ratio of the boys to that of the girls is 8:5.  How many more girls should join the school so that the ratio becomes 4:3?
a)25  b)50    c)100   d)200

12.A variable x varies directly as the cube of another variable y.if x=4,y=2,then find y  when x = 32
a)4   b)8     c)16    d)32

13.What should be subracted from both the numbers which are in the ratio 3:4 so that the ratio becomes 2:3
a)4   b)6     c)10    d)cannot be determined

14.A varies directly as the sum of the quantities B and C.B in turn varies directly as x and C varies inversely as x.When x=2,A = 6 and when x=4,A=9.Find the value of A when the value of x=16
a)2 1/2      b)1     c)8 1/2 d)32 1/4

15.The volume of a shere varies directly as the cube of its radius.If three cubes of radii 3  cm,4 cm and 5 cm are melted and recast into one sphere,then find the radius of the sphere
a)5.5 cm     b)6 cm  c)7 cm  d)7.5 cm
Directions for question 16 to 18:These questions are based on the data given below
There are two colleges in the town-college A and college B.There are 500 students more in college A than in college B.The ratio of the boys to that of the girls in college A is 3:2 and that in college B is 4:1.The ratios of the number of science,humanities and commerce students in college A and college B are respectively 2:5:3 and 2:3:3.The number of commerce students in both the colleges is the same.
16.How many students are there in college A?
a)2000      b)2500  c)3000  d)3500
17.How many girls are there in two colleges together?
a)1400      b)1600  c)1700  d)2000
18.How many more/less humanities students are there in college A than in college B?
a)400 more  b)400 less     c)500 less     d)500 more

19.If (2x+5):(7x-6) is the duplicate ratio of 5:8,then find the value of x
a)6  b)7     c)10    d)none of these

20.The mean proportional between two numbers is 16 and their third proportional is 128.Find the smaller of the two numbers
a)8  b)12    c)16    d)32

21.A bag contains 50 p,25 p and 10 p coins in the ratio 5:9:4,amounting to Rs 206.Find the  number of coins of each type
a)200,360,160       b)160,360,200  c)360,373,123  d)678,234,763

22.what is the ratio whose terms differ by 40 and the measure of which is 2/7?
a)16:56     b)14:56 c)15:56 d)16:72

23.A sum of Rs 53 is divided among A,B,C in such a way that A gets Rs 7 more than what B gets and B gets Rs 8 more than what C gets.The ratio of their shares is
a)16:9:18   b)25:18:10     c)18:25:10     d)15:8:30

24.A certain amount was divided between A and B in the ratio 4:3.If B's share was Rs 4800,the total amount was
a)Rs 11,200 b)Rs 6,400     c)Rs 19,200    d)Rs 39,200

25.If 10% of x = 20% of y,then x:y is equal to
a)1:2       b)2:1   c)5:1   d)10:1

26.x varies inversely as square of y.Given that y=2 for x=1.The value of x for y=6 will be equal to
a)3  b)9     c)1/3   d)1/9

27.The ratio of incomes of A and B is 5:4 and the ratio of their expenditures is 3:2.If at the end of the year,each saves Rs 1600,then income of A is
a)Rs 3400   b)Rs 3600      c)Rs 4000      d)Rs 4400

28.Three containers have their volumes in the ratio 3:4:5.They are full of mixtures of milk  and water.The mixtures contain milk and water in the ratio of (4:1),(3:1) and (5:2) resp.The contents of all these three containers are poured into a fourth container.The ratio of milk and water in the fourth container is
a)4:1       b)151:48       c)157:53       d)5:2

29.In a school,10% of the boys are same in number as 1/4rth of the girls.What is the ratio of
boys to girls in that school?
a)3:2       b)5:2   c)2:1   d)4:3

30.The ratio of number of boys and girls in a school is 3:2.If 20% of the boys and 25% of the
girls are scholarship holders,what percentage of the students does not get the scholarship?
a)56 b)70    c)78    d)80

31.The sides of a triangle are in the ratio 1/2:1/3:1/4 and its perimeter is 104 cm.The length of the longest side is
a)52 cm     b)48 cm c)32cm  d)26cm

32.which of the following ratios is greatest?
a)7:15      b)15:23 c)17:25 d)21:29

33.In a college the ratio of number of girls to boys is 8:5.If there are 160 girls,the total number of students in the college is
a)100       b)250   c)260   d)416

34.The least whole number which when subracted from both the terms of the ratio 6:7 gives a ratio less than 16:21 is
a)2  b)3     c)4     d)6

35.The speeds of three cars are in the ratio 5:4:6.The ratio between the time taken by them to travel the same distance is
a)5:4:6     b)6:4:5 c)10:12:15     d)12:15:10

36.15 litres of mixture contains 20% alcohol and the rest water.If 3 litres of water be mixed with it,the percentage of alcohol in the new mixture would be
a)15 b)16 2/3       c)17    d)none of these

37.20 litres of mixture contains milk and water in the ratio 5:3.If 4 litres of this mixture  be replaced by 4 litres of milk,the ratio of milk to water in the new mixture would be
a)2:1       b)7:3   c)8:3   d)4:3

38.85 kg of a mixture contains milk and water in the ratio 27:7.How much more water is to be added to get a new mixture containing milk and water in the ratio 3:1?
a)5kg       b)6.5kg c)7.25kg       d)8kg

39.The ages of A and B are in the ratio 3:1.Fifteen years hence,the ratio will be 2:1.Their present ages are
a)30,10     b)45,15 c)21,7  d)60,20

40.The average age of three boys is 25 years and their ages are in the proportion 3:5:7.The age of the youngest boy is
a)21 b)18    c)15    d)9

Ration and Proportion Examples


Exercise :
1. Divide Rs. 580 between A and B in the ratio of 14:15.
Soln:A:B = 14:15 => 580 is divided into 29 equal parts => each part = Rs. 20.
So A’s share = 14 parts = 14 x 20 = Rs. 280
B’s share = 15 parts = Rs. 300.
2.If A:B = 2:3 and B:C = 4:5 then find A:B:C.
Soln:
To combine two ratios the proportions common for them shall be in equal parts. Here the common proportion is B for the given ratios.
Making B equal in both ratios they become 8:12 and 12:15 => A:B:C = 8:12:15.
3. Three numbers are in the ratio of 3: 4 : 8 and the sum of these numbers is 975. Find the three numbers.
Soln:Let the numbers be 3x, 4x and 8x. Then their sum = 3x+4x+8x = 15x = 975 => x = 65.
So the numbers are 3x = 195, 4x = 260 and 8x  = 520.
4. Two numbers are in the ratio of 4 : 5. If  the difference between these numbers is 24, then find the numbers.
Soln:Let the numbers be 4x and 5x. Their difference = 5x – 4x = x = 24 (given).
So the numbers are 4x = 96 and 5x = 120.
5. Given two numbers are in the ratio of 3 : 4. If 8 is added to each of them, their ratio is changed to 5 : 6. Find two numbers.
Soln:Let the numbers be a and b.
A:B = 3:4 => A / B = 3 / 4.
Also, (A+8) / (B+8) = 5 / 6.
Solving we get, A=12 and B = 16
6. A garrison has provisions for 120 soldiers for 240 days. After 180 days 60 more soldiers will join the group. For how many more days will the provisions last?
Soln:Actually after 180 days,
If 120 members are there provisions come for 60 more days (since total 240 days)
But now 180 members are there.
So number of days = (120/180) X 60 = 40 days.
7. If 24 men working for 12 hrs a day can do a work in 16 days, in how many days can 8 men working 6 hrs a day do it?
Soln:24 men – 12 hrs – 16 days
8 men – 6 hrs – ? days (n)
n =16 X (12 / 6) X (24 / 8)    ( since no of hrs reduced no of days has to increase and no of men reduced also increases no of days i.e., inverse proportional)=> n = 96 days.
8. Two numbers are respectively 20% and 50% more than a third number. The ratio of the two numbers is:
A. 2 : 5 B. 3 : 5     C. 4 : 5       D. 6 : 7
Solution : Let the third number be x.
Then, first number = 120% of x =
120x
=
6x
100
5

Second number = 150% of x =
150x
=
3x
100
2

Ratio of first two numbers =
6x
:
3x
= 12x : 15x = 4 : 5.


9. A sum of money is to be distributed among A, B, C, D in the proportion of 5 : 2 : 4 : 3. If C gets Rs. 1000 more than D, what is B's share?
A.        Rs. 500            B.        Rs. 1500
C.        Rs. 2000          D.        None of these
Solution :
Let the shares of A, B, C and D be Rs. 5x, Rs. 2x, Rs. 4x and Rs. 3x respectively.
Then, 4x - 3x = 1000
x = 1000.
B's share = Rs. 2x = Rs. (2 x 1000) = Rs. 2000.
10. The ratio of the number of boys and girls in a college is 7 : 8. If the percentage increase in the number of boys and girls be 20% and 10% respectively, what will be the new ratio?
A.        8 : 9     B.        17 : 18
C.        21 : 22 D.        Cannot be determined
Solution : Originally, let the number of boys and girls in the college be 7x and 8x respectively.
Their increased number is (120% of 7x) and (110% of 8x).
120
x 7x
and
110
x 8x
100
100

42x
and
44x
5
5

The required ratio =
42x
:
44x
= 21 : 22.
5
5

Ratio and Proportion Key Points


Key Points :
Ratio:
The ratio of two quantities a and b in the same units, is the fraction and we write it as a : b.
In the ratio a : b, we call a as the first term or antecedent and b, the second term or consequent.
Eg. The ratio 5 : 9 represents
5
with antecedent = 5, consequent = 9.
9
Rule: The multiplication or division of each term of a ratio by the same non-zero number does not affect the ratio.
Eg. 4 : 5 = 8 : 10 = 12 : 15. Also, 4 : 6 = 2 : 3.
 Proportion:
The equality of two ratios is called proportion.
If a : b = c : d, we write a : b :: c : d and we say that a, b, c, d are in proportion.
Here a and d are called extremes, while b and c are called mean terms.
Product of means = Product of extremes.
Thus, a : b :: c : d (b x c) = (a x d).
Fourth Proportional:
If a : b = c : d, then d is called the fourth proportional to a, b, c.
Third Proportional:
a : b = c : d, then c is called the third proportion to a and b.
Mean Proportional:
Mean proportional between a and b is ab.
Comparison of Ratios:
We say that (a : b) > (c : d)    
a
c
.
b
d
Compounded Ratio:
The compounded ratio of the ratios: (a : b), (c : d), (e : f) is (ace : bdf).
Duplicate Ratios:
Duplicate ratio of (a : b) is (a2 : b2).
Sub-duplicate ratio of (a : b) is (a : b).
Triplicate ratio of (a : b) is (a3 : b3).
Sub-triplicate ratio of (a : b) is (a1/3 : b1/3).
If
a
=
c
, then
a + b
=
c + d
.     [componendo and dividendo]
b
d
a - b
c - d
Variations:
We say that x is directly proportional to y, if x = ky for some constant k and we write, x y.
We say that x is inversely proportional to y, if xy = k for some constant k and
we write, x
1
.
y