Triangle product puzzle

Algebra Level 3

In this puzzle, number written on every triangle equals the product of numbers written on three bottom triangle. Also every number must be a positive Integer greater than 1.

And A + B = 45 A + B = 45 ,

You need to find the value of 25 C A 1 B 2 25CA^{-1}B^{-2} .

Example for how this puzzle works is given here:

For the triangle with vertex at bottom, it works as follows:


The answer is 24.

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2 solutions

David Vreken
May 14, 2018

Label the missing triangles D D , E E , and F F , as shown below:

Then 2 E D = 12 2ED = 12 and 2 E F = 16 2EF = 16 , which simplifies to E D = 6 ED = 6 and E F = 8 EF = 8 . Since every number is a positive integer greater than 1 1 , E E must be a factor of 6 6 and 8 8 and greater than 1 1 , which means E = 2 E = 2 . Since E D = 6 ED = 6 and E F = 8 EF = 8 and E = 2 E = 2 , D = 3 D = 3 and F = 4 F = 4 .

We also know that 2 A F = B 2AF = B , and since F = 4 F = 4 , B = 8 A B = 8A . We are given that A + B = 45 A + B = 45 , and substituting B = 8 A B = 8A gives 9 A = 45 9A = 45 , which means A = 5 A = 5 . Since A = 5 A = 5 and B = 8 A B = 8A , B = 40 B = 40 .

Since C = 12 16 B C = 12 \cdot 16 \cdot B and B = 40 B = 40 , C = 7680 C = 7680 .

Therefore, 25 C A 1 B 2 = 25 7680 5 1 4 0 2 = 24 25CA^{-1}B^{-2} = 25 \cdot 7680 \cdot 5^{-1} \cdot 40^{-2} = \boxed{24} .

Hana Wehbi
May 14, 2018

We have 8 B = A A + B = 45 9 B = 45 B = 5 8B= A\implies A+B=45 \implies 9B=45 \implies B=5

Then A = 45 5 = 40 C = 12 × 16 × 5 = 960 A =45-5=40 \implies C=12\times 16\times 5= 960

The answer is 960 40 = 24. \frac{960}{40}=24.

I think the letters A and B must be switched in the equations.

B is the product of three triangles below it, so B = 2 * 4 * A = 8A. B = 8A is correct and A = 8B is not.

Vaibhav Priyadarshi - 3 years ago

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