What is the sum of the reciprocals of the triangular numbers?

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What is the sum of the reciprocals of the triangular numbers?

The most popular and authoritative arithmetic book in late 17th and 18th century England, it stayed in print for 100 years.

In baking a hemispherical loaf of bread of 10" radius, the crust was everywhere of an equal thickness, and the solidity of the crust was equal to half the solid content of the whole loaf. What were the dimensions of the interior soft part?

An analysis of James Gregory's proof of the Pappus-Guldin theorem, along with the original documents both in Latin and English.

Make of 10 three parts such that one part multiplied by 3 makes as much as the other multiplied by 4 and as the other multiplied by 5.

On a day in spring a boy has gathered cherry blossoms under a cherry tree. Nearby a poet is reading some of his poems aloud. As he reads, the boy counts out the cherry blossoms, one blossom for each word of a poem.

Given a number, take 1/3 of the number away from itself and add 2. If this result is multiplied by itself, it equals the number plus 24. What is the number?

A history of algebra from its early beginnings to the twentieth century.

A four-sided town measures 1100 feet on one side and 1000 feet on the other side, on one edge 600 and the other edge 600.

What is the sum of the following series, carried to infinity: 11, 11/7, 11/49, etc.?