Therefore: 101.9 MHz = 101.9 x 106 Hz = 1.019 x 108 Hz QUESTION: Which of the following is equivalent to 101.9 MHz? A. 1.019 x 106 Hz, B. 1.019 x 108 Hz, C. 1.019 x 104 Hz, D. 1.019 x 10-5 Hz “M” is the official abbreviation for the SI prefix “mega,” which means 1,000,000 or 106. Therefore: 101.9 MHz = 101.9 x 106 Hz = 1.019 x 108 Hz Other prefixes worth knowing: d = deci = 10-1, c = centi = 10-2, m = milli = 10-3,  = micro = 10-6, n = nano = 10-9, p = pico = 10-12 k = kilo = 103, G = giga = 109 SCRIPT Which of the following is equivalent to 101.9 megahertz? 1.019 times ten to the sixth hertz 1.019 times ten to the eighth hertz 1.019 times ten to the fourth hertz Or 1.019 times ten to the negative fifth hertz CLICK Upper case M is the official abbreviation for the SI prefix mega, which means one million, or ten to the power six. Therefore, CLICK 101.9 megahertz is equal to 101.9 million hertz, or 101.9 times ten to the sixth hertz. Since all the answers are given in standard scientific notation --- where the coefficient is a number between one and ten --- we move our decimal point two places to the left. By doing so, we make our coefficient 100 times smaller, so we need to make our power of ten a hundred times larger to maintain the value of our number. From 10 to the sixth, our power of ten becomes ten to the eighth. The correct answer is B. Here are some other SI prefixes that are quite commonly used. You should know these by heart. PAUSE 3 seconds. To answer this question, let’s count the number of significant figures for each of the choices given. Let’s start with choice D, which is written in scientific notation… BOX CHOICE D A number is written in scientific notation if it is written as a number between one and ten, which is called the coefficient HIGHLIGHT 1.5000 Times a power of ten HIGHLIGHT 10-3 If a number is written in scientific notation, then all the digits in the coefficient are significant. HIGHLIGHT the word “coefficient” HIGHLIGHT 1.500 Therefore, there are four significant digits in choice D….. One, five, zero, and zero CALLOUT “4 s.f.” next to choice D Let’s take a look at the other choices, which are not written in scientific notation. In these cases, the first significant digit is the first nonzero digit --- that is… the leftmost nonzero digit. For choice A, the first significant digit is one ---- HIGHLIGHT 1 For choice B, the first significant digit is two ---- HIGHLIGHT 2 For choice C, the first significant digit is three --- HIGHLIGHT 3 Now, if the number has a decimal point, as in choices A and C, then all digits to the right of the first significant digit are also significant. HIGHLIGHT “If number has decimal point…. “ on slide So, in choice A, the numbers zero, five, and zero are also significant. HIGHLIGHT 0, 5, and 0 as they are called out) Choice A has four significant figures…. CALLOUT “4 s.f.” next to choice A In choice C, the numbers one, zero, and zero are significant… So, choice C has four significant figures…. CALLOUT “4 s.f.” next to choice C Finally, let’s take a look at choice B, which is not in scientific notation and does not have a decimal point. HIGHLIGHT “if there is no decimal point….” in slide The rule in this case is that trailing zeros may.. Or may not be significant. HIGHLIGHT last two zeros in 20700 It is customary to assume the worse --- that is… that they’re not significant. Therefore, if unless we are given information to the contrary, only two, zero, and seven are significant in choice B. There are 3 significant figures in choice B. CALLOUT “3 s.f.” next to choice B. The correct answer is B. It has only three significant figures… the other choices have four significant figures.

Video ID: 1A-1-1 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08