Question

A box contains 20 equal-sized balls, numbered 1 to 20. Two balls are drawn at random simultaneously. What is the probability that the numbers on the two balls will differ by more than 2

Answer 1

Answer:

P = 0,7947       or    79,47%

Step-by-step explanation:

We have 20 balls, the total possible outcomes drawn two balls simultaneously is:

C =  m! /n! *( m - n )!

C = 20!/2! *( 20 - 2)!

C= 20*19*18!/ 2* 18!

C  =  20*19/2

C = 190

Now the number of successful outcomes x ( those where balls differ by more than 2 is)

x = total numbers of outcomes  -  20  ( outcomes differing in 1 ) - 19 (outcomes differing in 2 )

x =  190 - 39

x = 151

Then the probability  of drawing tw balls with numbers differing n mr than two is

P = successful outcomes / total outcomes

P = 151/190

P = 0,7947       or    79,47%