Exams

Let father's age be x year and son's age be y year.

According to question,

2(x+y) = 8y _______(I)

and (x+y)/2 = 30

=> x+y = 60 years__________(II)

From equation (I) and (II)

8 y = 120

y = 15 years,

Hence x = 45 years.

First ten odd numbers form an arithmetic progression of the form
1,3,5,7,9......
here a = first term = 1
d = common difference = 2
Average of first n numbers = (2a + (n - 1)d)/2
n th term of the AP = a + (n - 1)d
Substituting a = 1, d = 2 and n = 10 in the above formulas
average of first 10 numbers = 10
10 th term of the AP = 19
Therefore average of first 10 terms is 19 - 10 = 9 greater than
the last term. Hence the average is greater than the sum by
9/19 X 100 = 900/19 %

Ans. 
Let B’s investment = x rs.
∴ A’s investment =( x + 1200) rs.
Ratio of the profits of A and B = (x+1200)*(15+4):x*15 = {19(x+1200)}:15x
Now,let the total profit of A =y
∴ total profit of B = (y-280)
But total profit = 1240
⇒y+(y-280)=1240
⇒2y=1520
⇒y= 760
∴profit of A = 760rs.
Profit of B = 760-280=480 rs.
Ratio of profits= 760:480 = 19:12
According to the question,

19(x+1200)/15x = 19/12

12x+14400 = 15x

⇒3x = 14400
⇒x = 4800 rs.
⇒investment of A = 4800+1200
                          = 6000 rs.

Perimeter of the rectangle is given by 3000/10 = 300 mts

But we know,

The Perimeter of the rectangle = 2(l + b)

Now,

2(8x + 7x) = 300

30x = 300

x = 10

Required, Area of rectangle = 8x x 7x = 56 x 100 = 5600 sq. mts.

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