Answer:0.6
Explanation:
Given
Bowl contains 4 red and 2 Green balls
Probability of selecting two red balls given atleast one of the ball is red + Probability of selecting two red balls given that no ball is red =1
Probability of selecting two red balls given that no ball is red 


Required Probability
Answer:
Time taken, 
Explanation:
It is given that, a small metal ball is suspended from the ceiling by a thread of negligible mass. The ball is then set in motion in a horizontal circle so that the thread’s trajectory describes a cone as shown in attached figure.
From the figure,
The sum of forces in y direction is :


Sum of forces in x direction,

.............(1)
Also, 
Equation (1) becomes :

...............(2)
Let t is the time taken for the ball to rotate once around the axis. It is given by :

Put the value of T from equation (2) to the above expression:


On solving above equation :

Hence, this is the required solution.