Average Questions

 Required average = [(76 * 16) - (75 * 10)] / 6 = (1216 - 750)/6 = 466/3 = 233 /3.

Let the side of the square plot be 'a' ft.
Given area of the plot (a x a) = 289 => a = 17
Length of the fence = Perimeter of the plot = 4a = 68 ft.
Cost of building the fence = 68 x 58 = Rs. 3944.

 Clearly, to find the average, we ought to know the number of boys, girls or students in the class, neither of which has been given.

So, the data provided is inadequate.

Four tenths = 0.4

Five thousandths = 0.005

The average is (0.4 + 0.005)/2 = 0.2025

Use unitary method:

In  hours, 123 typists can type 984 paper

In 1 minute, 123 typists can type   = 246 papers

In 1 minute, 1 typist can type  =2 papers      [ Hint  hours = 4 minutes]

Clearly, we  have : x = (3y + 3z ) / 6 or 2x = y + z.

Let the number of boys = x

From the given data,

=> [21x + 16(18)]/(x+16) = 19

=> 21x - 19x = 19(16) - 16(18)

=> 2x = 16

=> x = 8

Therefore, the number of boys in the class = 8.

The third proportional of two numbers p and q is defined to be that number r such that

p : q = q : r.

Here, required third proportional of 10 & 20, and let it be 'a'

=> 10 : 20 = 20 : a

10a = 20 x 20

=> a = 40

Hence, third proportional of 10 & 20 is 40.