**3 years ago, the average 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:**

A.5 years

B.2 years

C.1 year

D.4 years

Answer

Option (b) is correct

**Explanation** **–**

Total age of 5 members, 3 years ago = (17 x 5) years = 85 years

Total age of 5 members now = (85 + 3 x 5) years = 100 years

Total age of 6 members now = (17 x 6) years = 102 years

Age of the baby = (102 – 100) years = 2 years

**Of the four numbers, the first is twice the second, the second is one-third of the third and the third is 5 times the fourth. The average of the numbers is 24.75. The largest of these numbers is:**

A.45

B.25

C.30

D.45

Answer

Option (d) is correct

**Explanation** **–**

Let the fourth number be a

then, third number = 5a, second number= 5a/3 and first=10a/3

a+ 5a+ 5a/3 + 10/3 = 24.75 x 4

so,a=9

So, the numbers are 9, 45, 15 and 30

**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:**

A. 1 : 4

B. 2 : 3

C. 3 : 4

D. 4 : 2

Answer

Option (b) is correct

**Explanation** **–**

Let the ratio be k:1

Then, k x 16.4 + 1 x 15.4 = (k + 1) x 15.8

(16.4 – 15.8) k = (15.8 – 15.4)

k=2/3

**The average price of 10 books is Rs. 12 while the average price of 8 of these books is Rs. 11.75. Of the remaining two books, if the price of one book is 60% more than the price of the other, what is the price of each of these two books?**

A.Rs 10 and Rs 16

B.Rs 12 and Rs 24

C.Rs 24 and Rs 18

D.Rs 28 and Rs 12

Answer

Option (a) is correct

**Explanation** **–**

Total price of the two books = Rs. [(12 x 10) – (11.75 x 8)] = Rs. (120 – 94) = Rs. 26

Let the price of one book be Rs.x

Then, the price of other book = Rs. (x + 60% of x )= x + (3/5)x= (8/5)x

so, x +(8/5)x=26 , x=10

The prices of the two books are Rs. 10 and Rs. 16

**The average age of 30 boys of a class is equal to 14 years. When the age of the class teacher is included the average becomes 15 years. Find the age of the class teacher?**

A.50

B.44

C.45

D.42

Answer

Option (c) is correct

**Explanation** **–**

Total ages of 30 boys = 14 x 30 = 420 years

Total age when class teacher is included = 15 x 31 = 465 years

Age of class teacher = 465 – 420 = 45 years

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