Art of Problem Solving: 2012 AMC 10 B #25 / AMC 12 B #22

Art of Problem Solving's Richard Rusczyk solves 2012 AMC 10 B #25/AMC 12 A #22.

[@hatchguy444]

Also, since this is AMC, after being done with level X, I think we can choose option E because it's the only multiple of 5.

[@name-np4gr]

the way richard moves his finger along the paths is so smooth 😍😍

[@srikanthtupurani6316]

nice problem. it is easy but there is a high chance of making calculation mistake. it is painful to loose marks due to calculation mistakes. we cannot use generating series here. i dont see any way to use polynomials here.

[@alexwang982]

Srikanth Tupurani Just find the multiple of 5

[@victorialiao4695]

so funny and informative! lovin' it!

[@raymondxu8961]

thanks! you helped me a lot!

[@woojae1000]

He's awesome

[@shibamroy102]

sorry 20=2400

[@Tommy2804]

great professor!!!

[@firefwing24]

@elflordbob1 Chuck Testa

[@shibamroy102]

first comes 5+5+5+5=20 so it would be multiple of 2, =2400

[@lukeqiao5477]

Wait i don't think that is correct. I think it should be a multiple of 5 because you need to multiply by 5 to get the number of ways. The only answer choice is E because 2400 is the only multiple of 5. You got the right answer but I don't think you used the right method.

[@tekkitlitecraft8723]

@@lukeqiao5477 I think he meant multiple of 20