Anderson's game of 24

Petr and Jon are playing a guessing game. Petr thinks of 2 integers ( a , b ) (a, b) , each of which are from 0 to 10, and tells Jon their product. If Petr says that the product is 24, how many distinct ordered pairs of integers could Petr be thinking of?

This problem is posed by Anderson A .

Details and assumptions

For an ordered pair of integers ( a , b ) (a,b) , the order of the integers matter. The ordered pair ( 1 , 2 ) (1, 2) is different from the ordered pair ( 2 , 1 ) (2,1) .


The answer is 4.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

13 solutions

Akshat Jain
Oct 16, 2013

Let's take out the prime factors of the given number 24 24 , which are 2 × 2 × 2 × 3 2 \times 2 \times 2 \times 3 . These can be arranged in the forms of pairs-

2 × 12 2 \times 12 , 3 × 8 3 \times 8 and 4 × 6 4 \times 6 .

But we have to choose pairs which have numbers between 0 0 and 10 10 .

Thus, we get only two pairs- 3 × 8 3 \times 8 and 4 × 6 4 \times 6 .

Since this question asks for the number of ordered pairs, we can form two more pairs from these two pairs, giving us a total of 4 \fbox{4} pairs.

Genius

Debjyoti Chattopadhyay - 7 years, 6 months ago

Don't miss out ( 1 × 24 ) (1 \times 24) in the pairs,though it is not required here.

A Brilliant Member - 7 years, 7 months ago

Log in to reply

Oh yes, missed that. Really sorry.

Akshat Jain - 7 years, 7 months ago

1x24 2x12 3x8 4x6

fred fan - 7 years, 7 months ago

oh yeah missed that

fred fan - 7 years, 7 months ago

24 is the multple of 2,3,4,6,8 which r d integers between 0 to 10..now of these nmbrs,(3,8),(4,6),(6,4),(8,3) this pair of nmbrs cmplts d givn cndtion..the ans is 4 pair of integers cmplts d condition

Saikat Patra - 7 years, 7 months ago
Daniel Chiu
Oct 13, 2013

We find the number of ordered pairs of factors from 0 to 10. We find these: ( 3 , 8 ) (3,8) ( 4 , 6 ) (4,6) ( 6 , 4 ) (6,4) ( 8 , 3 ) (8,3) The answer is 4 \boxed{4} .

Why are these all the pairs? Did you have to look at all the 100 possible products?

Calvin Lin Staff - 7 years, 7 months ago

Log in to reply

I found factors of 24: (1,24), (2,12), (3,8), (4,6), and the reverses.

Only these four have both factors below 10.

Daniel Chiu - 7 years, 7 months ago

Is this factoring? :D

Ako Yu - 7 years, 8 months ago
Fajrul Falah
Oct 14, 2013

First, reach the factor of 24 24 , that is; 2 , 3 , 4 , 6 , 8 , 12 , 24 2,3,4,6,8,12,24

Because the integers that thought by Petr is between 0 0 to 10 10 , and the product of them is 24 24 .

So the number, and its possible ''structure'' is: 3 , 8 3,8 4 , 6 4,6 6 , 4 6,4 8 , 3 8,3

There is 4 4 possible

I did this with permutations. Total ordered pairs = 4 ! 3 ! 1 ! \frac {4!}{3! 1!}

A Former Brilliant Member - 7 years, 8 months ago

Log in to reply

I'm not too sure how you did it with permutations. Just because you got the correct numerical answer doesn't mean that the logic was correct.

Your formula looks like the combination ( 4 1 ) {4 \choose 1} , in which case you are choosing one value of 3 , 4 , 6 , 8 3, 4, 6, 8 , and the other one is fixed. However, you need to justify why the rest do not work.

Calvin Lin Staff - 7 years, 7 months ago

why not 1*24

Arnav Rupde - 7 years, 7 months ago
Shubham Gupta
Oct 17, 2013

There are 4 combinations of 2 numbers whose product is 24 from 0 to 10 , ie. (3,8) , (8,3), (4,6) and (6,4).

Nurin Zunah
Oct 13, 2013

It can be 3x8, 8x3, 6x4 or 4x6

is it Petr or Jon who is thinking this numbers....

Jonas Kgomo - 7 years, 8 months ago
Devesh Rai
Oct 13, 2013

Since it is given that integers are from 0-10 then possible product of integers are 8 3 and 6 4.But distinct ordered possible pair of integers are - (3),(4),(6),(8) so correct answer is 4 if you count it.Here 83 and 64 means product of 8,3 and 6,4

Anzar Aznzar
Mar 30, 2014

24= 8 * 3 = 6 * 4

( 8 , 3 ) , ( 3 , 8 ) , ( 6 , 4 ) , ( 4 , 6 )

Yash Bhagwat
Feb 2, 2014

(3,8)(8,3)(4,6)(6,4)

Prasun Biswas
Dec 21, 2013

The factors of 24 are 1,2,3,4,6,8,12,24. Now, we can see that the ordered pairs satisfying this are (1,24),(24,1),(2,12),(12,2),(3,8),(8,3),(4,6) and (6,4).

But, it is also said that for the ordered pair (a,b), we have a and b can range from 0 to 10. So, the ordered pairs (1,24),(24,1),(2,12) and (12,2) does not satisfy this. So, these pairs does not belong in the solution set.

Only 4 ordered pairs, i.e, (3,8),(8,3),(6,4) and (4,6) belong in the solution set, so no. of required ordered pairs = 4 =\boxed{4}

HamzAh Rana
Oct 19, 2013

integers r frm 0 to 10.... so 24 is our product\ possible factors are 8 3 or 4 6... then (4,6),(8,3)...total 4 integers! Ans= 4

The answer is =(3 x 8),(4 x 6) = (8 x 3),(6 x 4) = These are the 4 pairs whose product is 24.{between 0 to 10}

Gopala Krishna
Oct 15, 2013

In between 0 and 10, there is only possible to take 8,3 and 4.6 pairs for the product 24. If we interchange we get 4 pairs. i.e., (8,3), (4,6), (3,8), (6,4).

나 가수
Oct 14, 2013

Different factors of 24 are; (24,1) - (12,2) - (8,3) - (6,4) = 4 unlike ordered pairs.

Just to clarify, what are the ordered pairs? Are they the 4 that you listed?

Calvin Lin Staff - 7 years, 7 months ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...