# Convergence articles

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A compilation of ethnomathematical ideas from around the world.

An elementary introduction to Euler squares and how they can be used in teacher training

What is the perpendicular height of a cloud when its angles of elevation were 35 degrees and 64 degrees as taken by two observers?

Page 11: Dantzig to Dieudonne

Determine the radii of three equal circles described within and tangent to a given circle, and also tangent to each other.

This is the title page of the 1640 printing of Galileo's Operation of the Geometrical and Military Compass, originally published privately in 1606. Galileo had invented a version of this geometrical compass a few years earlier and evidently gave copies of this manual to those who bought the compass. The compass had many uses, from performing square root calculations to determining ranges of cannons to solving surveying problems.

The steamer, Katie, leaves the wharf at New Orleans and runs an average speed of 15 mph. When Katie had gone 25 miles, the steamer R.E. Lee leaves the wharf and runs the average speed of 18 mph. How far will the Lee go before she overtakes the Katie?

A man bought a number of sheep for $225; 10 of them having died, he sold 4/5 of the remainder for the same cost and received$150 for them. How many did he buy?

A merchant gave a university 2,814 ducats on the understanding that he was to be paid back 618 ducats per year for 9 years, at the end of which the 2,814 ducats should be considered as paid.

Two travelers, starting at the same time from the same point, travel in opposite directions round a circular railway.