quants-average-quiz2

Average Quiz-2

Dear Readers,

Maths is an important subject in CLAT,DULLB & Other Law Exams. In any of law exam, Maths carries weightage of 20 -25 % of questions. With focused practice good marks can be fetched from this section. These questions are very important in achieving your success in CLAT, DULLB and Other Law Exams..

Q1.The average age of a group of friends is 34 years. If five new friends with an average age of 30 years join the group, the average age of the entire group becomes 32 years. How many people were there in the group initially?

•  4
•  5
•  6
•  7

Solution

Old combined age = 34x

New combined age

= (5 + x) x 32 = 34x + (5 x 30)

Þ 32x + 160 = 34x + 150

\ x = 5 

Q2. If 20 kg of wheat costing Rs 16 a kg is mixed with Rs, 16 kg of a second variety of wheat costing Rs 25 a kg, then what is the average cost of the resulting mixture?

•  25
•  24
•  22
•  20

Solution

Avg = (20 x 16 + 16 x 25)/ (20 + 16)

= 720/36 = 20 

Q3. If two kinds of grapes costing Rs 16 a kg and Rs 21 a kg are mixed in the ratio of 2 : 3 then find the cost of mixture per kg?

•  17
•  20
•  18
•  19

Solution
Avg = (16 x 2 + 21 x 3)/ (2+3) = 95/9 = 19 

Q4.  If 15 litres of 20% alcohol is mixed with 2 litres of 24% alcohol, then find the concentration of the resulting solution?

•  588/97   
•  588/27   
•  588/57   
•  588/7   

Solution
            (15 x 20+ 12 x 24)/(15 + 12) = (588)/ 27 

Q5.Find two numbers whose AM is 12.5 and GM is 10?

•  20,15
•  18,24
•  20,5
•  12,16

Solution
 a + b = 25; ab = 100

a + 100/a = 25

Þ a² + 100 - 25a = 0 Þ a² - 25a + 100 = 0

Þ a² - 20a - 5a + 100 = 0

Þ a(a-20) - 5(a-20) = 0

Þ (a-5)(a-20) = 0

Therefore, a = 5 or a = 20

If a = 5; b = 20

If b = 20; a = 5 

Q6. The average age of a husband and his wife was 23 years at the time of their marriage. After five years they have one-year old child. The average age of the family now is:

•  19 years
•  73 years
• 28.5 years
•  29.3 years

Solution
New avg. age=((23+23)+(5+5)+1}/3 =19

Q7. The average salary of all the workers in a workshop is Rs. 8000. The average salary of 7 technicians is Rs.12000 and the average salary of the rest is Rs. 6000. The total number of workers in the workshop is:

•  20
•  21
•  22
•  23

Solution

8000 =  {(7X12000)+(xX6000)}/(x+7)

8x + 56 = 84 + 6x

Þ x = 14.

Hence Total number of workers are 7+14 = 21 

Q8. 3 years ago, the average age of a family of 5 members was 17 years. A baby having been born, the average age of the family is the same today. The present age of the baby is

•   1 years
•   11/2 years
•   2 years
•   3 years

Solution

Combined age of family 3 years ago = 5x17 = 85

Combined age of family now = 6 x 17 = 102

Baby’s age,

Þ 102 = 85 + 5 x 3 + b         \ b = 2 

Q9.In an examination, a pupil's average marks were 63 per paper. If he had obtained 20 more marks for his. Geography paper and 2 more marks for his History paper, his average per paper would have been 65. How many papers were there in the examination?

•  8
•  9
•  10
•  11

Solution

Old avg. = 63

New avg. = 65

Let n be number of papers

65n = 63n + 20 + 2    Þ n = 11 

Q10.The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ratio of the number of boys to the number of girls in the class is:

•  1 : 2
•  2 : 3
•  3 : 4
•  3 : 5

Solution

            Let n be ratio of boys to girls

15.8 = (16.4n+15)/(n+1) Þ .6n = .4 Þ n = 2/3

[Alternatively] B:G = x:y

[(16.4)(x)+(15.4)(y)]/(x+y) = 15.8(x+y)

x:y = 2:3