Figuring Out Celsius-Fahrenheit

Thank you for revealing your secret formulas for converting Celsius to Fahrenheit and vice versa; (+40 x 9/5 -40) and (+40 x 5/9 -40) respectively.

I agree they are easier to remember than the traditional formulas, but they are certainly not easier to use. Not only is one more step required in the computation, but adding 40 to the number to be converted gives a larger number to be multiplied by the fraction, thereby adding to the problem’s difficulty. In the final analysis, your formula is not easier to do mentally because multiplying by 5/9 or 9/5 is difficult to do using pencil and paper, or with a calculator; and doing it mentally is a feat beyond most of us.

For practical purposes, we need to remember only the formula for changing Celsius to Fahrenheit; and we need a formula that we can do in our heads while walking or driving down the street and can’t wait for the Fahrenheit temperature to flash on the time and temperature sign above the bank. I am happy to say that I have a solution to this overwhelming problem.

I make the conversion using a simplified formula of the traditional (x 9/5 +32). I simply multiply by 2 and add 30. The 2 comes from rounding 9/5 to 10/5, which reduces to 2; and 30 is used instead of 32 to compensate for the enlarged fraction.

This formula gives an exact conversion at 50 degrees, but at 60 degrees it is one degree over the exact figure, at 70 degrees it is two degrees over, etc. Once you know the pattern, you can adjust downwards to get a nearly exact answer.

For example: To convert 26 degrees Celsius to Fahrenheit, multiply by 2, which gives 52. Add 30, giving 82. Adjust downwards 3 degrees to 79. The exact answer is 78.8.

I have done many such mental calculations while driving down the street or waiting for a red light to change. I have also tried your formula, which is hopeless when, after adding 40, the sum cannot be divided by 5. Unfortunately, most numbers fall into this category.

Your readers now have three options:

1--The traditional formula: (x 9/5 +32)

2--Your secret formula: (+40 x 9/5 -40)

3--My simplified formula: (x 2 +30)

Conceptually, I prefer the traditional formula. Memory wise--I prefer your formula. But for everyday convenience, mine can’t be beat.

SONIA APPELL

Agoura