Date: 09/16/97 at 00:42:42 From: Aubin Subject: Scientific notation How do you do this problem? I don't understand how you're supposed to get the answer: 5x10 to the 3rd power = 5,000 5x10 to the -3rd power = -5,000 Is this correct?
Date: 11/03/97 at 09:56:46 From: Doctor Pipe Subject: Re: Scientific notation Aubin, The first part of what you wrote is correct; 5x10 to the 3rd power = 5,000. The second part is not correct. Writing a negative exponent, such as 10^-3 (read that as ten to the minus third power) is the same as writing 1/(10^3) (read that as one over ten to the third power). Notice that the exponent is negative when writing 10^-3 and positive when writing 1/(10^3) - yet the two numbers are equal. Remember that any number to the zeroeth power, say 10^0, is equal to 1. 10^0 = 1; 5^0 = 1; 275^0 = 1. Remember also that when multiplying two numbers written as base^exponent, if the base in both numbers is equal then we add together the exponents: 10^5 x 10^6 = 10^(5+6) = 10^11. If we have a number 10^5, what number do we multiply it by to get 1? Well, 10^5 x 10^(-5) = 10^(5 + (-5)) = 10^0 = 1. So if 10^5 x 10^(-5) = 1 then 10^(-5) = 1 / 10^5 So, since 10^3 = 1,000 then 10^(-3) = 1/(10^3) = 1/1,000 = 0.001 . It follows from this that: 5x10 to the -3rd power = 5 x 10^(-3) = 5 x 0.001 = 0.005 . The reason for this can be seen by examining what numbers to the right of the decimal point represent. You know what numbers to the left of the decimal point represent: the units digit represents the numeral times 10^0 (any number to the 0th power is 1), the tens digit represents the numeral times 10^1, the hundreds digit represents the numeral times 10^2, and so on. Well, to the right of the decimal point, the tenths digit represents the numeral times 10^-1, the hundredths digit represents the numeral times 10^-2, the thousandths digit represents the numeral times 10^-3, and so on. It's important to understand exponents because exponents allow us to extend the range of numbers that we can work with by allowing us to easily write and work with very large and very small numbers. It's so much easier to write: 10^23 then to write: 100,000,000,000,000,000,000,000 Or to write: 10^(-23) instead of: 0.00000000000000000000001 Good luck and enjoy! -Doctor Pipe, The Math Forum Check out our web site! http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994-2013 The Math Forum