A computer science problem by Thành Đạt Lê

Computer Science Level 1

$\boxed{\phantom0}\ \boxed{\phantom0}\ \boxed{\phantom0}\ \boxed{\phantom0} \times 3 = \boxed{\phantom0}\ \boxed{\phantom0}\ \boxed{\phantom0}\ \boxed{\phantom0}\ \boxed{\phantom0}$

Can we fill in the boxes with distinct digits so that the equation is satisfied?

Clarification: The above equation represents a 4-digit number multiplied by 3 to produce a 5-digit number, so the leftmost box is non-zero on either side.

Yes No

1 solution

Daniel Branscombe
Aug 15, 2017

There are 15 possible solutions:

$4609*3=13827$

$5683*3=17049$

$5694*3=17082$

$5823*3=17469$

$5832*3=17496$

$5934*3=17802$

$6358*3=19074$

$6819*3=20457$

$6839*3=20517$

$6918*3=20754$

$8169*3=24507$

$8369*3=25107$

$9046*3=27138$

$9136*3=27408$

$9168*3=27504$

Please tell the methods

Aditi Parmar - 3 years, 9 months ago

exhaustive search, there is a very small number of possible values for the 4-digit number, so it was a simple matter of checking which ones resulted in a valid solution. Namely there are 9 9 8*7=4356 possible values for the 4-digit number.

Daniel Branscombe - 3 years, 9 months ago

So is this more of a Computer Science problem? Or is there a direct way to arrive at a solution?

Geoff Pilling - 3 years, 9 months ago

I think it's CS, I've converted it. If I saw an elegant approach, then I'll convert it back.

Pi Han Goh - 3 years, 9 months ago

I don't know, if I asked how many possible solutions are there, it's definitely computer science. This problem were asked for 5th graders. A kid handed the paper to me and said: "Could you solve this for me? I have to go to school. I will give you candies after school." How cute!

Thành Đạt Lê - 3 years, 9 months ago

A computer science problem by Thành Đạt Lê

1 solution

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