SOLUTION: two numbers are selected at random from 1 to 9 find the probability that their sum is even?
Algebra.Com
Question 737654: two numbers are selected at random from 1 to 9 find the probability that their sum is even?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
two numbers are selected at random from 1 to 9 find the probability that their sum is even?
-----
Consider a 9 by 9 array of these pairs.
----
Consider the sum of each of the 81 pairs in the array.
----
The 1st row of sums looks like: 2,3,4,5,6,7,8,9,10::::: 5 even : 5 odd
the 2nd row of sums looks like: 3,4,5,6,7,8,9,10,11:::: 4 even : 5 odd
The 3rd row of sums looks like: 4,5,6,7,8,9,10,11,12::: 5 even : 5 oddc.
etc
etc
etc
-------------
# of even sums is 5+4+5+4+5+4+5+4+5 = 41
=======
P(sum is even) = 41/81
============================
Cheers,
Stan H.
RELATED QUESTIONS
Two game tiles, numbered 1 through 9, are selected at random from a box without... (answered by ikleyn)
The two digits are selected at random from the digits 1 through 9. If the sum of the two... (answered by Edwin McCravy)
Two distinct even numbers are selected at random from the first ten even numbers greater... (answered by venugopalramana)
Two digits are selected at random from digits 1 through 9, if 2 is one of the digits... (answered by Alan3354)
Select 3 numbers at random from 1 to 9. What is the probability that the sum of 3 numbers (answered by gwendolyn)
a bag contains eleven discs numbered 1 to 11. two discs are selected at random with... (answered by stanbon)
Ten cards are numbered 1 to 10. Three different cards are selected at random from these... (answered by Edwin McCravy)
From numbers 3,5,5,7,7,7,9,9,9,9 one numbers is selected at random find the probability... (answered by macston)
Ten cards are numbered from 1-10.
Three different cards are selected at random from... (answered by ewatrrr)