17-year-old Helena Muffly wrote exactly 100 years ago today:
Tuesday, September 24, 1912: It is raining now. I guess or was. Had an exam in Geometry. Took up Arithmetic today. Didn’t have to but I chose to do so.
Her middle-aged granddaughter’s comments 100 years later:
High school courses apparently were only a month of so long a hundred years ago.
I wonder why Grandma decided to take Arithmetic if it wasn’t required. Maybe she enjoyed doing mental math.
Here are two mental math tricks for adding fractions that I found in a hundred year old textbook:
Example 1: Add two fractions whose numerators are 1.
Solution: Add the denominators, and place the sum over the product of the denominators.
Example 2: Add two fractions whose numerators are alike and greater than 1.
Solution: Add the denominators and multiply the sum by the numerator of either of the fractions, and write the product over the product of the denominators.
Source: Kimball’s Commercial Arithmetic (1911)
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