What Frequency is Needed for Helium to Produce the First Harmonic in a Tube?

[phys232]

Homework Statement

A 256 Hz tuning fork produces the first harmonic in a tube filled with air and having one closed and one open end. If the tube were filled with helium where the speed of sound is 965 m/sec, what frequency would be needed to produce the first harmonic? Assume the speed of air at the same temperature is 330 m/sec.

Homework Equations

v=lambda*f

The Attempt at a Solution

I have tried:

f=256 Hz, speed of helium=965m/s
lambda=v/f=965/256=247040m
f=v/lambda=965Hz/247040m=0.0039Hz

 

[magwas]

Simple calculus error. you don't expect the result of division of two numbers in the same order of magnitude be 3 orders of magnitudes away.
Just get your calculator, and push those buttons carefully.

We all make silly mistakes. I am writing small scripts for all serious calculations, and carefully observe all intermediate results for sanity.
Still most of my calculations have problems. I have lost my old rigidity in math. You are just gaining it.