5 ## FRACTIONSTO MEASURE something requires the name of a number. But the names of the natural numbers are not sufficient, because what we measure will not always be a multiple of the unit of measure, that is, of 1. In order to measure we have to create numbers that are parts of 1. Those are the fractions. What is more, in a natural number, the units are indivisible. We therefore must extend the idea of a "number" so that it corresponds to things that we measure, that is, things that are continuous. Let 1 therefore now be the measure of a continuous unit: 1 inch, 1 meter, 1 hour; and let us imagine that we have to invent a numeral -- a symbol, a "number" -- for half of 1. What symbol should we invent?
But why? Because of the ratio of 1 to 2. Since 1 is
"one-half." In fact, we What is our understanding of "2"? It is twice as much as 1. What is "3"? It is three times 1. And the number we write
We know every number according to its ratio to 1, which is the source. A fraction that is less than 1 we call a proper fraction. And in English, the proper fractions have the same names as the ratio of the numerator to the denominator.
ratio of 2 to 3. 2 is two thirds of 3. That fraction, moreover, is the measure of the length that has the
The fraction called "two-thirds" is two thirds of 1. (Notice that we write the name of the fraction hyphenated, but not the name of the ratio. In that way we maintain the distinction between fractions and ratios. A fraction is a number; a ratio is a relationship between numbers and between lengths.) The same ratio to 1 Every fraction has a ratio to 1: the same ratio that the numerator has to the denominator.
Problem 1. a) What number is the fourth part of 1? Write its symbol and also write its name in words. To see the answer, pass your mouse over the colored area.
b) When we speak of a fourth of 1, does '1' refer to a continuous unit or
Continuous.
Because of the ratio of 2 to 5. 2 is Problem 3. What ratio has each number to 1?
Problem 3. a) What is a proper fraction?
A fraction that is b) How can we recognize a proper fraction? The numerator is less than the denominator. c) What is a mixed number?
A whole number plus a Problem 4. Continuous versus discrete Answer with a mixed number, or with a whole number and a remainder, whichever makes sense. a) It takes three yards of material to make a skirt. How many skirts can 8 skirts. 1 yard will remain. 8 1/3 skirts makes no sense. Skirts are discrete. b) You are going on a journey of 25 miles, and you have gone a third of 8 1/3 miles. That is, 25 ÷ 3. Here, the mixed number makes sense. We need mixed numbers for measuring. Problem 5. What is an improper fraction. A fraction greater than or equal to 1. Recall from arithmetic that we can always express a mixed number as an improper fraction. Problem 6. Express 6½ as an improper fraction.
Problem 7. Complete each proportion with natural numbers.
e) .49 : 1 = 49 : 100. Multiply both terms by 100. f) 2.5 : 1 = 25 : 10. Multiply both terms by 10. Copyright © 2017 Lawrence Spector Questions or comments? E-mail: themathpage@yandex.com Private tutoring available. |