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

Explanation – Let the fourth number be a

then hen, 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

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

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

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

Explanation – Let the number of passed candidates be a

Then total marks =>120 x 35 = 39 a + (120 – a) x 15

4200 = 39 a + 1800 – 15 a

a = 100

Explanation – The total of 11 results = 11 x 50 = 550

The total of first 6 results = 6 x 49 = 294

The total of last 6 results = 6 x 52 = 312

The sixth result is common to both:

Sixth result = 294 + 312 – 550 = 56

Explanation – Total age of all members = 6 x 22 = 132 years

7 years ago, total sum of ages = 132 – (6 x 7) = 90 years

But at that time there were 5 members in the family

Average at that time = 90 /5 = 18 years

Explanation – Let the average after 16th innings be a, then total score after 17th innings =>

16a+85 = 17 (a+3)

a = 85-51 = 34

Average after 17 innings = a + 3 = 34 + 3 = 37

Explanation – Suppose the average expenditure was Rs a.

Then total expenditure = 35a

When 7 more students join the mess, total expenditure = 35a + 42

Now, the average expenditure= (35a+42) / (35 + 7)

Now, we have (35a + 42)/ 42 =(a – 1)

or, 35a + 42 = 42a – 42

7a = 84

a = 12