
Probability and Statistics Basic Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
January 10th, 2018, 08:27 AM  #1 
Newbie Joined: Jan 2018 From: India Posts: 1 Thanks: 0  Need help to solve below problems?
1) If a fair coin (a coin which shows heads or tails with equal probabilities when tossed) shows heads upon tossing, 4 numbers are selected from 1, 2, 3, ... 100 (a number once selected is not selected again) and if tails shows up, 3 numbers are drawn from 3, 6, 9, 12, ... 99 (a number once selected is not selected again). Determine the probability of the event that the sum of the selected numbers is even. 2) Iron deficiency is known to exist in 28%, 14% and 5% of the people of three different tribes T1, T2 and T3 respectively. All the three tribes have equal population. An investigator selects a person from one of the tribes randomly, from the total population of the three tribes and examines for iron deficiency. It turns out that the selected person does not have the deficiency. Determine the probability that this person belonged to tribe (i) T1, (ii) T2, (iii) T3. 
January 10th, 2018, 08:52 AM  #2 
Senior Member Joined: May 2016 From: USA Posts: 1,119 Thanks: 464 
With respect to three numbers, if all three are odd, the sum is odd. If only two are odd, the sum is even. if only one is odd, the sum is even. And if none is odd, the sum is even. So GIVEN that three numbers are selected, what are the respective probabilities that all three are odd and that only one is odd? So GIVEN that three numbers are selected, what is the probability that their sum is odd? Now do the same analysis for four numbers. GIVEN that four numbers are selected, what is the probability that their sum is odd? Now what? 
January 10th, 2018, 11:19 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 19,506 Thanks: 1741  
January 10th, 2018, 02:21 PM  #4 
Senior Member Joined: May 2016 From: USA Posts: 1,119 Thanks: 464  

Tags 
problems, solve 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Please Solve this 4 EPIC Problems.... i couldn't solve it myself  gen_shao  Algebra  12  November 2nd, 2014 06:11 AM 
How to master maths  should we solve simple problems or variety of problems?  joshis1  Algebra  2  October 10th, 2014 03:55 PM 
Can somebody help solve this problems please  vloraboy  Algebra  3  April 2nd, 2009 01:05 PM 
CAN SOMEBODY HELP SOLVE THIS PROBLEMS PLEASE  vloraboy  Algebra  1  February 21st, 2009 05:02 PM 
Three problems to solve  Rooonaldinho  Math Events  10  October 28th, 2007 08:17 AM 