Two different 2-digit numbers are randomly chosen and multiplied together. What is the probability that the resulting product has a units digit of 1?
There are: 90 nCr 2 =4005 possible products.
Only 153 of them end in "1"
Therefore, the probability = 153 / 4005 = 17 / 445
So the probability will be 4/100 = 0.04 (I have fixed a typo) Thanks guest
Hi Melody: I think they want "Two different 2-digit numbers are randomly chosen and multiplied together."
My original answer (the one you referred to) does look at the multiplication of 2 two digit numbers
The header row is the units digit of the first number
The header column is the units digit of the second number.
What I did not take into consideration is that the numbers are supposed to be different from one another.
This makes the question much more difficult. Each cell will no longer occur an equal number of times.
So I have redone it. I think this method is right but I am less confident than i was with the original answer.