Calculating the Speed of Waves in a Vibrating String and Resonant Pipe

[JSmithDawg]

Homework Statement

A 0.13-m string, fixed at both ends and vibrating in its n = 4 harmonic, excites a pipe that is 0.88 m long and open at both ends, into its second overtone resonance. What is the speed of transverse waves on the string? The speed of sound in air is 345 m/s.

Homework Equations

F=nv/(2L)

The Attempt at a Solution

I wasn't present when my class went over this, so keep in mind that this is just my speculation. Anyway, as the string excites the pipe, the frequencies of both waves should be the same.
f₁=f₂
I don't know the velocity of the first wave, but the velocity of the second wave should be the speed of sound. Now, plugging in numbers I know, I get
4(v)/(2*.13m)=3(345 m/s)/(2*.88m)
v=67.6 m/s

The online quiz I'm doing is telling me this is wrong, so what's wrong with my logic?

 

[TSny]

4(v)/(2*.13m)=3(345 m/s)/(2*.88m)
v=67.6 m/s

I don't get 67.6 m/s when solving your equation for v.