The Australian Air Force Hid Its Recruitment Phone Number In An Unsolvable Maths Puzzle

The Royal Australian Air Force last week published an impressively complicated maths formula online. It invited engineers to solve the problem to find a phone number to call and apply for a job.

Defence Force recruiters obtained the formula from a University of Melbourne professor. Business Insider Australia understands it was intended as a means of driving engagement, and not a formal test.

That’s good, because the formula – which involves infinite sums, integrals, complicated trigonometry and imaginary numbers – doesn’t produce the intended phone number.

Defence Force Recruiting has corrected the formula since this story was originally published.

Here was the original formula:

The first four terms in the formula produce the Defence Jobs phone number, 131901, when added together.

The remaining terms are intended to equal zero, but two typos have made that impossible:

The formula works if you replace sin 2 x with sin(2x) in the third-last line, and (2k-1)! with (2k+1)! in the second-last line.

Update 6:15pm: Defence Force Recruiting has now updated the formula.

“Our original formula included two small typos, which we have now fixed,” an Air Force marketing manager told Business Insider on Thursday afternoon.

“We hope people still enjoy the inherent fun and hidden challenges. Our thanks go to the eagle-eyed Reddit users who spotted them first; you are exactly the kind of people we’d be looking for.”

The RAAF hires aeronautical, airfield, armament and electronics engineers with Bachelor of Engineering qualifications. Degree-qualified engineering recruits get a starting salary of $78,100 a year and financial assistance for further, post-graduate studies.

Undergraduate engineering students may also apply to join the Air Force via the Australian Defence Force Academy.

The Australian Defence Force puts job applicants through a two-day recruiting process, including interviews with a career counsellor, nurse, psychologist, doctor and military staff member.

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