Numbers
They can be positive or negative, odd or even. They can be whole or in parts. Without them you wouldn’t be able to tell the time. You wouldn’t even know how old you are. And how about this—without them you wouldn’t have any math homework!
What are they? They’re numbers. And you use them every single day.
WHAT IS A NUMBER?
A number is a word or a symbol. It usually represents an amount, such as 3 keys in your pocket or a bill worth 5 dollars. Numbers are used for all kinds of things. They’re on clocks and cash registers, on thermometers and license plates. You see them on road signs and calendars.
WHO USES NUMBERS?
Everyone uses numbers sometimes, but some people use numbers a lot. Scientists use numbers to describe the size of distant galaxies or to calculate the paths of rocket ships in space. Accountants use numbers to keep track of money. Baseball fans use numbers to measure how well players are doing. And that’s just a small sample of the ways we use numbers.
WHOLE NUMBERS
The numbers we see and use most often are called whole numbers. These are numbers such as 1, 6, or 12. But believe it or not, whole numbers are only one of several kinds of numbers.
NEGATIVE NUMBERS
A negative number is a whole number that is less than zero. Negative numbers are only used for certain kinds of measurements. You can’t hold -2 pears in your hand! But you can give 2 pears to someone else, so that you have 2 less than you did before. When it’s really cold outside, the temperature can be -6 degrees Fahrenheit. Or a running back in football might have 6 carries for -13 yards (if he’s having a bad day).
FRACTIONS
Have you ever eaten half of an apple? Then you’ve eaten a fraction of an apple. A fraction is a number that represents just a part of something, not the whole thing. Fractions are not whole numbers. That half an apple you ate can be written like this: y of an apple. The apple was divided into 2 parts and you ate 1. If you ate a quarter of a pizza, you’d be eating ‚ of it (1 part in 4). Got it? A fraction is created by dividing one whole number by another.
PRIME NUMBERS
Mathematicians are scientists who study math. For them, prime numbers are one of the most interesting types of numbers. A prime number can only be evenly divided by two whole numbers: itself and the number 1.
Take 7 for example: 1 × 7 = 7, right? But that’s the only way you can multiply two numbers get exactly 7, so 7 is a prime number. Now take 8: 1 × 8 = 8, but so does 2 × 4. So 8 is not a prime number. Prime numbers are so special that they have been used to create secret codes!
UNIVERSAL LANGUAGE
One way to think about numbers is as the universal language of science. It doesn’t matter what language you speak, numbers and math work the same way even if the symbols are different. Numbers allow scientists from different countries to share their work and to advance understanding, even if they speak completely different languages.
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Science
