Probability of Same Last Digit Product of Random Integers

Keep in mind this is for two digits. If the problem was for two numbers, the chances would be much higher, about 40%.In summary, the probability that two integers chosen at random and their product will have the same last digit is 4%. This is based on the condition that the two integers end in 0, 1, 5, or 6, and that their product also ends in the same digit. The chances are even higher if the problem is for two numbers instead of two digits, with a probability of about 40%.
  • #1
zorro
1,384
0

Homework Statement



The probability that two integers chosen at random and their product
will have the same last digit is?

The Attempt at a Solution



According to the given condition, the last digit should be 0,1,5 or 6. Now what is the next step?
 
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  • #2


Abdul Quadeer said:

Homework Statement



The probability that two integers chosen at random and their product
will have the same last digit is?

The Attempt at a Solution



According to the given condition, the last digit should be 0,1,5 or 6. Now what is the next step?
Is there any information about how large the two integers are?
 
  • #3


You can't choose two integers "at random", supposedly meaning with equal probability. There are infinitely many integers. You need to specify a probability distribution function.

Also, what given condition? What is special about 0,1,5, and 6?
 
  • #4


Mark44 said:
Is there any information about how large the two integers are?

No.

LCKurtz said:
Also, what given condition? What is special about 0,1,5, and 6?

I think you did not understand the question (may be its wording is not correct).
If you select numbers which end with any of the above digits, say 25 and 75, their product 1875 also contains the same last digit '5', which is the required condition.
 
  • #5


Abdul Quadeer said:
No.



I think you did not understand the question (may be its wording is not correct).
If you select numbers which end with any of the above digits, say 25 and 75, their product 1875 also contains the same last digit '5', which is the required condition.

I still don't understand the question. Apparently you could phrase it as:

"Pick two digits randomly and independently from {0,1,2,...,9}. What is the probability that their product contains the same last digit?"

But what if the two chosen digits are different? What does the "same last digit" mean then?
 
  • #6


LCKurtz said:
I still don't understand the question. Apparently you could phrase it as:

"Pick two digits randomly and independently from {0,1,2,...,9}. What is the probability that their product contains the same last digit?"

But what if the two chosen digits are different? What does the "same last digit" mean then?
I would interpret the problem in a similar way, with this revision:

"Pick two digits randomly and independently from {0,1,2,...,9}. What is the probability that the two digits are the same and their product contains the same last digit?"

If that interpretation is correct, then you have 0 * 0 = 0, 1 * 1 = 1, 5 * 5 = 25, and 6 * 6 = 36.
 
  • #7


it can be any two integers. How large the number is doesn't matter. If both integers end in a 0, 1, 5, or 6, the conditions will be met. So the first random integer is a 4/10 chance. and the second is a 1/10 chance.

4/10 * 1/10 = 1/25. Therefore there is a 4% chance.
 
  • #8


dacruick said:
it can be any two integers. How large the number is doesn't matter. If both integers end in a 0, 1, 5, or 6, the conditions will be met. So the first random integer is a 4/10 chance. and the second is a 1/10 chance.

4/10 * 1/10 = 1/25. Therefore there is a 4% chance.

Perfect! Thats the answer provided. I understood it now. Thanks!
 
  • #9


Abdul Quadeer said:
Perfect! Thats the answer provided. I understood it now. Thanks!

Cheers
 

FAQ: Probability of Same Last Digit Product of Random Integers

What is probability and why is it important in math?

Probability is a mathematical concept that measures the likelihood of an event occurring. It is important in math because it allows us to make informed decisions and predictions based on the likelihood of different outcomes.

What are the basic principles of probability?

The basic principles of probability include the sample space, event, and probability function. The sample space is the set of all possible outcomes, the event is the specific outcome we are interested in, and the probability function assigns a numerical value to each event to represent its likelihood of occurring.

How do you calculate probability?

To calculate probability, we use the formula P(E) = n(E)/n(S), where P(E) is the probability of event E occurring, n(E) is the number of outcomes in event E, and n(S) is the total number of outcomes in the sample space.

What is the difference between theoretical and experimental probability?

Theoretical probability is based on mathematical calculations and assumes that all outcomes are equally likely. Experimental probability is based on actual data from experiments or observations and may differ from theoretical probability due to chance or other factors.

How can probability be applied in real-life situations?

Probability can be applied in various real-life situations, such as predicting the weather, making financial decisions, and analyzing data in scientific experiments. It can also help us understand and evaluate risks and make informed decisions in everyday life.

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