# Daniel Bobrow, 1964

## The gas consumption of my car is 15 miles per gallon. The distance between Boston and New York is 250 miles. What is the number of gallons used on a trip between Boston and New York?

What does ‘gas consumption’ mean? What is a gallon? What is a car?

Bobrow’s program has no concept about such things. It does have about 100 rules about how words like ‘and’, ‘per’ and ‘number of’ may relate to an equation. Thus, in some sense it knows that ‘per’ means ‘find two numbers and compute their quotient’.

Bill’s father’s uncle is twice as old as old as Bill’s father. 2 years from here, Bill’s father will be three times as old as Bill. The sum of their ages is 92.Find Bill’s age.