Quantitative Aptitude - Arithmetic Ability Questions

Let A be the event that X is selected and B is the event that Y is selected.

P(A) = 1/7,  P(B) = 2/9.

Let C be the event that both are selected.

P(C) = P(A) × P(B) as A and B are independent events: 

       = (1/7) × (2/9)  = 2/63

Let Rs.x be the amount that the elder daughter got at the time of the will. Therefore, the younger daughter got (3,500,000 - x).

The elder daughter’s money earns interest for (21 - 16) = 5 years @ 10% p.a simple interest.

The younger daughter’s money earns interest for (21 - 8.5) = 12.5 years @ 10% p.a simple interest.

As the sum of money that each of the daughters get when they are 21 is the same,

 x+5*10*x100=3,500,000-x+12.5*10*3,500,000-x100

 x+50x=3,500,000-x+125100*3,500,000-125x100

 2x+50x100+125x100=3,500,000*1+54

 200x+50x+125x100=94*3,500,000

 =>x=2,100,000=21 lakhs

Let the number of students in the class be 100 and let this required average be x.

Then, (10 * 95) + (20 * 90) + (70 * x) = (100 * 80)

=> 70x = 8000 - (950 + 1800) = 5250

=> x = 75.

pool : kerosene 

   3  :  2(initially) 

   2  :  3(after replacement)

 Remaining QuantityInitial Quantity=1-Replaced QuantityTotal Quantity

(for petrol)   23=1-10k

 => K = 30

 Therefore the total quantity of the mixture in the container is 30 liters.