Using The Pocket Calculator (1978)

Millions of people use pocket calculators every day. They may be used in drafting or by sales people in showrooms. There are hundreds of different uses for calculators and a surprising variety of specially designed calculators to do certain jobs. There are calculators that are programmable just like a computer. Others are designed to handle scientific work, accounting, or banking. You can even find calculators that fit your wallet or that have clocks. >> Clear. >> And would you believe that there are even calculators that can talk? >> Four. Nine. Six equals >> They're built specifically for blind people. Except for talking, they work the same way as other calculators. >> Seven equals six. Three point zero Clear. Nine. >> But with all the different styles and features available, how can you pick out the right personal calculator for yourself? First, you should have some idea of what you want it to do and how much you can afford to spend. You'll probably want one that can at least add, subtract, multiply, and divide. There are other things to consider in choosing a calculator for yourself. For instance, it's nice to have keys that click. So that when you push a key, you know that you've entered the number. You'll probably want it to be strong, so that if you accidentally drop it, it won't break. You may want it to be an algebraic calculator, so you can enter the problem in the same way that you would work it on paper. There are other kinds. If you should choose a different type of calculator, you'll need to learn how to operate it from the store clerk where you bought it, or from your teacher. No doubt you'll want a good warranty, so that if your calculator goes bad, you can send it back and get it repaired rapidly and economically. Make sure that the display is easy to read. Some calculator displays are harder to read than others. And make sure that the calculator's keys fit your fingers easily. No particular kind is better than another. It's up to you and what you're looking for in a calculator. When you get a new calculator, you'll want to see how it works. You can start with a simple addition problem. 26 + 49 Before you start any computations, always press the clear key. To add these two numbers, you first enter the number 26 in your calculator. To do this, press the key labeled two, and then press the key labeled six. Now the number 26 is shown in the display. Next, press the plus sign. Now you enter the other number, 49, by pressing the four key and the nine key in that order. Notice that the number in the display is now 49. Now that you've entered both numbers, you just push the equal key and the answer to the problem, 75, appears in the display. Now suppose that you have three or more numbers to add. The problem is 43 + 37 + 22. To work this one, you go about it the same way. You enter the first number, 43, by pushing the four key and the three key. Then press the plus key. The next number to be added is 37. So, you enter it by pressing the three key and the seven key. Then push the plus key. The last number to be added is 22. Enter it by pressing the two key twice. Now that all the information has been fed into the calculator, the final step is to push the equal key and the correct answer appears as 102. Now that you've mastered adding with the pocket calculator, we can move on to the next function, subtraction. But remember, before starting a new problem, always press the clear key to get rid of any numbers that may be stored in your calculator. Subtraction is done the same way as addition, but using the minus key instead of the plus. To work this problem, we enter the first number, 297. To do this, you press the two key, nine, and the seven. The number you've entered, 297, now appears in the digital display. Since this is a subtraction problem, you press the minus key. Next, enter the remaining number, 137, by pressing the one, three, and seven keys in that sequence. The number 137 should appear in the display. Now, all you need to do is press the equal key, and the answer appears in the display as 160. Here's a real-life subtraction problem. Suppose you have 297 football trading cards and give away 76 of them. The problem would be 297 minus 76 equal. Press the keys in the correct order, and you get the answer, 221. You'd have 221 football cards left. But, be careful. Sometimes subtraction problems come out with negative numbers. Try 37 minus 47, and the display will show minus 10. Now, let's try a multiplication. The problem is 67 * 47 equal. Just as in addition and subtraction, you begin by entering the first number, 67. Press the six key and then the seven key. Now, since this is a multiplication problem, press the times key. You're multiplying 67 * 47, so you enter the 47 in the calculator by pressing the four and the seven keys. After pressing the equal sign, the answer, 3,149, shows up on the display. Let's try a multiplication problem in a grocery store. If you know that there are 72 packs of pop and six cans to a pack, how many are there all together? By multiplying 72 * 6 on the calculator, the answer is there are 432 cans of pop. But be careful. You may multiply numbers that give an answer larger than your calculator will display. If the number is too large, the calculator's display will either flash the numbers on and off or flash a line of E's. If the number is too large, you'll have to find another way to work the problem. Another function that the calculator performs is division using the divide key. Division problems are solved in a similar manner to addition, subtraction, and multiplication problems. Suppose you want to divide 923 by 46. You enter the numbers in the same way you have with the other functions, 9 2 3 divide 4 6 equal. If you have an eight-digit calculator, the answer shows up as 20.065217. Let's try another division problem. Suppose you have 438 trading cards that you want to divide equally among six friends. The problem is stated 438 divided by 6 equal. So, using the calculator, you enter 4 3 8 push the divide key, enter 6, and push the equal key. The answer is 73. So, 73 cards would go to each of your friends. Now that you know how to perform the four basic functions with your calculator, addition, subtraction multiplication, and division let's try something a bit more complicated. Here's the problem. 36 - 21 * 43 + 62 / 3. If you work this problem across from left to right on the simplest calculators as you've done in the previous problems, you'll get the wrong answer. Let's try it that way. She enters 3 6 2 1 * 4 3 + 6 2 / 3 = The calculator displays 235.66666. That's not correct. Can you guess why the answer is wrong? She ignored the parentheses. In solving this kind of problem, you have to work the parts in the parentheses first. You do the problem in several steps starting from the left. First, enter 36. Subtract 21 on the calculator. The answer is 15. Record the 15 on a worksheet. Then clear the calculator. And add 43 + 62. The answer is 105. Write down 105 on the worksheet and clear the calculator. Now, using the calculator, you multiply 15 * 105. 41575. You write down 1575 on the worksheet. Then divide the 1575 by 3 and the correct answer is 525. If you're using a more complex calculator that's equipped with parenthesis keys, you can work this problem in just one step if you make certain to use the parenthesis when entering the problem in your calculator. Many calculators are equipped with a percent key. Calculating percentages can be a very useful function. For example, suppose you saw a new racing bike that cost $175. It's advertised at 15% off plus 5% tax. How much would it cost? Here's the way the problem would be stated. But in order for your calculator to handle the problem correctly, it will need to be treated like this. Notice that the 175 minus 15% is placed within parenthesis to be worked separately. You would enter one seven five minus one five and press the percent key. At this point, push the equal key. The answer appears as 148.75. This means that at 15% off the retail price of $175, the bicycle would cost 148.75. But now you have to add the 5% tax. The 148.75 is already in the calculator. So, you just press the plus key, then five, then the percent key, and finally, the equal key. The answer is 156.1875, or $156.19 is the total price of the bicycle. Other function keys are the square root and square of a number keys. If you wish to find the square root of a number such as 64, enter 64, push the square root key, and the answer is eight. Or if you wanted to square a number, you use the X squared key. Let's enter eight and square it. The answer is 64. So, you can see that the square root key and the square key, in a sense, cancel each other. To see this, let's try 5 squared is 25. The square root of 25 is five. Many calculators also have memory keys. If you have this type, find out how your particular model works. But in the meantime, you can use the basic functions you've already learned to do many things. For example, suppose you wanted to quickly find out how many minutes there are in a year. That's a big number. There are 365 days in a year, times 24 hours in a day, times 60 minutes in an hour, equals 525,600 minutes in a year. So, hard or long computational problems are made simple. When your parents go shopping, you could go along and calculate the best buys in the grocery store. For example, the best unit prices on different sizes of detergent. Or you might add up the grocery bill as you go. You could also use the calculator to check your math homework. But be sure to get permission from your teacher before using your calculator to work school math assignments. Remember, no matter what kind of calculator you use, you still need to know how to add, subtract, multiply, and divide because you must know how to set up the problems. So, don't become too dependent on your calculator. A calculator is fast, accurate, can handle large numbers, and it is fun to operate. But it takes a trained person to make it perform properly. You. >> Mhm.