Solving the troll riddle visually | Algebra II | Khan Academy

Solving the system of equations visually. Now we can save the prince/princess

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[billnbobfilms]

sry sal u solved the problem but in 11 minutes. Into the water you go!

[hockeyfanovechkin]

Thanks Sal for this, I now clearly understand how to solve systems of equations, especially through graphing!!!!

[mjuo]

f+t=900 x5
5f+10t=5500 x1
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5f+5t=4500
5f+10t=5500
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5t=1000
t=200
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f+t=900
f+200=900
f=700
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t=200
f=700
Simultaneous Equations.

[serrenblaze]

I've got simple solution for this. Multiply the either number by the total. 5x900 = 4500 and 10x900 = 9000. Take the difference of that to the ending value (1000 and 3500) and divide them both by the difference of the starting numbers (5) 1000/5=200 and 3500/5=700. 200 10's and 700 5's
Thank you for this video

[bigsexypanda]

I like that you put it in coordinates, did you just put the equations as lines in your calculator and solve for where they met?

[MarkAkAMarkinator]

Just practise using the method Khan used. Start out with basic problems like this and it will become even easier then trail and error.

[jules]

This is nothing short of amazing, like magic but actually real. My dumb empirical mind thought at first that there would be multiple solutions to this.

[thascrazy]

i love how the combination of these two videos are longer than 10 min. Sal would be in the river by now

[nagakalyan]

I did not expect this solution graphically, its amazing. I ended speechless

[samanthavo-]

i love this narrator. he's such a perfectionist and artist

[buckstarchaser]

My problem is that using a graph to find a specific number just seems so inaccurate that I somehow blocked myself from learning how to use them. How would you perform this process with a graph that required a precise decimal instead of a simple whole number?

[GKSTR]

Troll's response: You are correct but I haven't met my pushing adventurers into the river quota for the month... so umm yea this is awkward...

[RobertNugent]

Unfortunately, the adventurer couldn't finish before nightfall and he didn't have a torch.
.
You are eaten by a grue.

[nicsheffer]

Yes you could solve this with trial and error but if you were faced with something and the answer was 1.56239 of one and 5.65245876532 of the other good luck randomly guessing those numbers. Good luck finding that intersection by eye on a graph too. Easier to just learn to solve the equations. However the graph is a good representation of how to think about the problem and would work if you had a calculator that could graph and find the intersection. More challenging puzzles please!

[Perplexxed]

I feel like nobody ever cares about his masterpiece-level drawings, he could've been the mathematical Leonardo da Vinci.

[RonaldhoIsAWanker]

Its actually not too bad. Watch it a 2nd or 3rd time if you have to. The lightbulb will and off and it will "Click" eventually

[Faxtro]

The point isn't to have a challenging puzzel, if I'm correct. It's to teach those who need a simpler puzzel for the time being.

[GostosoSPbr]

Sal, this has more tham 1 responses right?
I got 650 = 3250 ($5) & 225 = 2250 ($10)

[thepurplelefant]

The max that the troll can have is 9000. (If he had all 10 dollar bills). For each 5 dollar bill his money goes down by 5. He has 3500 less than max so he has 700 5 dollar bills.

[iAreSoro]

Exactly what i was thinking, no need for all the graphs lol