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Math Puzzle for September 5, 2025

If the sun never sets at 40,000 feet, does aging stop as well?

Alameda Post - a drawing of a plane at sunset [1]
Stock image by DepositPhotos [2].

An airliner is on a course of 270 headed directly to San Francisco International Airport. The co-pilot is watching the evening sun and notices that it seems to be hovering. The altimeter indicates 40,005.13619 feet MSL (Mean Sea Level). SFO is 37.78° north latitude and the sun is holding steady above the horizon.

Find the true airspeed (TAS) of the airliner, given no appreciable winds.

(Hint: The radius of Earth is 3,960 miles; ignore any aircraft Mach limits.)

Correct answers sent to [email protected] [3] could win a Tucker’s gift card.

Last week’s winner [4] was James Forakis with A = 22698.007 square meters.

Jeff Smith is a former Math teacher and a retired US Navy Lieutenant Commander. Reach him at [email protected] [3].