Quantitative Aptitude - Arithmetic Ability Questions

since it is a combination = 38C17 = 2878 x 10^10

As the distance travelled is constant, the time taken is inversely proportional to speed.

Let 'u' be the speed of the current and 'v' be the speed of the boat.

Speed of the boat downstream = v + u & upstream = v - u

=> v+u/v-u = 30/20 => v/u = 5 => v = 5u

=> v + u = 6u = 10/20/60 miles/hr

=> 6u = 30 m/h

=> u = 5 m/h

Ayush's present age = 10 years.
His mother's present age = (10 + 20) years = 30 years.
Ayush's father's present age = (30 + 5) years = 35 years.
Ayush's father's age at the time of Ayush's birth = (35 - 10) years = 25 years.

Therefore Ayush's father's age at the time of marriage = (25 - 2) years = 23 years.

Let Akhil's weight = p kg

=> Shreyon's weight = 2p kg

Nani's weight = 0.9 x 2p = 1.8p kg

=> Arun's weight = 1.4p kg

Required percentage = 1.4p1.8p x 100

= 77.8%

~= 78%

Speeds of two trains = 30 kmph and 58 kmph

=> Relative speed = 58 - 30 = 28 kmph = 28 x 5/18 m/s = 70/9 m/s

Given a man takes time to cross length of faster train = 18 sec

Now, required Length of faster train = speed x time = 70/9  x  18 = 140 mts.

 4×3.14×r2 : 4×3.14×r2 = 1 : 2  

   0.125125...... = 0.125¯ =   125/999

P(getting prize) = 10/ (10 + 25) =2/7