Manhattan address algorithm

The Manhattan address algorithm is a series of formulas used to estimate the closest east–west cross street for building numbers on north–south avenues in the New York City borough of Manhattan.

Algorithm
To find the approximate number of the closest cross street, divide the building number by a divisor (generally 20) and add (or subtract) the "tricky number" from the table below:

Examples
For example, if you are at 62 Avenue B, $$62 \div 20 \approx 3$$, then add the "tricky number" $$3$$ to give $$6$$. The nearest cross street to 62 Avenue B is East 6th Street.

If you are at 78 Riverside Drive, $$78 \div 10 \approx 8$$, then add the "tricky number" $$72$$ to give $$80$$. The nearest cross street to 78 Riverside Drive is West 80th Street.

If you are at 501 5th Avenue, $$501 \div 20 \approx 25$$, then add the "tricky number" $$18$$ to give $$43$$. The nearest cross street to 501 5th Avenue is actually 42nd Street, not 43rd Street, as the Manhattan address algorithm only gives approximate answers.