Aptitude and Reasoning Questions

Number of ways of choosing 2 black pens from 5 black pens in 5C2 ways.

Number of ways of choosing 2 white pens from 3 white pens in 3C2 ways.

Number of ways of choosing 2 red pens from 4 red pens in 4C2ways.

By the Counting Principle, 2 black pens, 2 white pens, and 2 red pens can be chosen in 10 x 3 x 6 =180 ways.

We know that Cubes with no surface painted can be find using x-23, where x is number of cuttings. Here x=6.

 ∴ 6-23=64

Frequency of step of A:B:C = 5 : 6 : 7

But in terms of size of step, 6A = 7B = 8C

Therefore, Ratio of speeds of A, B and C = 5/6 : 6/7 : 7/8 = 140 : 144 : 147

The new numbers formed are 571, 352, 693, 814, 729

The second highest number is 729, its first digit is 7

Efficiency of P= 100/20= 5% per hour  

Efficiency of Q= 100/25= 4% per hour  

Efficiency of R= 100/40= 2.5% per hour  

Efficiency of S=100/50= 2% per hour 

Cistern filled till 10 am by P, Q and R  

Till 10.00am Pipe P filled 20%Till 10.00am Pipe Q filled 8%Till 10.00am Pipe R filled 2.5%30.5%  

Thus, at 10 am pipe P,Q and R filled 30.5% of the cistern. 

Rest of cistern to be filled = 100 - 30.5 = 69.5%  

Now, the time taken by P,Q,R and S together to fill the remaining capacity of the cistern 

= 69.5 / (5+4+2.5+2) = 5 Hours and 9 minutes(approx).

Therefore, total time =4 hrs + 5hrs 9 mins = 9 hrs and 9 mins

It means cistern will be filled up at 3:09 pm

let the radius of the pool be Rft

Radius of the pool including the wall = (R+4)ft

Area of the concrete wall = πR+42-R2=πR+4+RR+4-R = 8πR+2 sq feet

=> 8πR+2 = 1125πR2 =>11R2 =200R+2

Radius of the pool R = 20ft

The number of exhaustive outcomes is 36.
Let E be the event of getting an even number on one die and an odd number on the other. Let the event of getting either both even or both odd then = 18/36 = 1/2
P(E) = 1 - 1/2 = 1/2.