Part 6, Chapter 1, Algebra 1

Service Description

Grandma's Place of Natural Learning goes on with conversation about letters for names of things as "h" for "hours," in the book "E-Z ALGEBRA." ""What exactly does the expression 10Xh mean?" the professor asked. "I'd be more comfortable about accepting the expression if we clarified that." "The letter h is a symbol that stands for the number of hours," the king said. "It is a very general symbol, because we can apply it to a wide variety of specific circumstances. In any particular situation, we fill in the appropriate value of h. Once we have filled in the value, the expression 10Xh turns into a regular arithmetic expression, and we know how to calculate those. For example, if h is 20 in a particular case, then the expression 10Xh becomes 10X20, which is 200." "The letter h acts just like the word 'king,'" the professor realized. "The word 'king' by itself is a general term that does not refer to a particular person, just as the letter h is a general symbol that does not refer to a particular number. But in a specific situation you can specify which person you mean by 'king,' just as in a specific situation you can specify which number you mean by h." Recordis still objected to the unfamiliar, uncomfortable concept of using letters to stand for numbers. "How can you tell which letter you should use?" he demanded. "We can use whatever letter we feel like using," the professor said. (We did later adopt some guidelines to tell us what letter we would normally want to use. We decided that we would use a letter from the beginning of the alphabet, such as a, b, or c, to stand for a general 'known' quantity. We decided to use letters from near the end of the alphabet, such as x, y, or z, to stand for an "unknown' quantity that we were trying to find the correct value for. There are also some cases where the letter to use is obvious from what it is supposed to represent; for example, we will often use t to represent time, r to represent radius, w to represent width, and n to represent the number of objects in a particular group.") (Grandma will keep typing in another part to continue.)