Lesson 1: TI30xs Calculator

THE SCIENTIFIC CALCULATOR

The teacher at the machine shop will ask all the new students to use a hand calculator to find answers to many problems in mathematics. The kind of calculator they have chosen is called a scientific calculator, because it helps scientists solve the math problems of science. Machine shop work is not science, but it uses the discoveries of science and some of the mathematics of science.

GO NOW AND GET YOUR TI30xs CALCULATOR

Now that you have the calculator, let’s look at what it can do.

Orientation to the calculator:

• Liquid Crystal Display (LCD): The LCD is the gray window the top of the calculator; this window is also called the display. When you use the calculator, you will see the input data (the numbers you a working with) and the results (your answers) in the display.

• Solar Power Window: Below the LCD window is another window which uses light from the sun or from a lamp to make power to run the calculator. Be sure to leave this window uncovered, so you don’t block out the light. The calculator also uses a special battery for power. This batter should be replaced every 6 years by taking the calculator to the dealer. The power of the calculator will stay on for 6 minutes and then will tum off (in order to save the batteries). To tum it back on, simply press the red AC key, as described below.
• Red Keys:
  • The AC key (all clear): This key has two uses.
    1. The first use is to turn on the calculator. When you press the AC key, a “0.” will appear in the LCD window.

2. The second use of the AC key is to clear the LCD of numbers and answers, when you want to start over and return to “0.”

• • The C key (clear): This key will cancel the last number that you put in. (We will practice this in just a moment.)

• Number Keys: To the left of the red keys are the number keys:

  • 7	8	9
    4	5	6
    1	2	3
    0

  • When you press these keys the numbers will appear in the LCD window. The window will hold up to 8 digits.
• Mathematical Operation Keys and Equal sign: Directly below the Red Keys are the operation keys and the equal sign.

  • ×	÷
    +	–
    =

  • For example, when you want to multiply 3 x 4, you press the 3 key, then the x key, then the 4 key, and finally the equal (=) key.

• The decimal point key: The key is located in the bottom row, to the right of the 0 key.
  • With this key you can do operations using decimals. Use the decimal point key, • , to place the decimal point numbers you are working with.
  • Example: 14.475 + 137.25 + 233.685 = 385.41 (Press 1, 4, decimal point, 4, 7, and 5; then press + and then the next numbers, etc.)

• Using the C key and the backspace key to change mistakes in data entry; (the backspace key is located directly above the 8 and is shown as an arrowhead). Either of these keys can be used to cancel a number which you have entered and now wish to change, without losing the numbers you have entered for the calculation.
  • For example, I wish to multiply the two number 3.4 and 56. I enter 3.4, then the x sign, then 53 (mistake); I wish to change the 53 to 56 without starting all over again.
    • I can change this by either of two ways:
      1. Using the C key: Before pressing the = sign, press the C key, then enter 56, then press =.

2. Using the Backspace Key: As above, you wish to multiply 3.4 x 56, but you type 53 instead of 56. You can correct this mistake by backspacing one space; this will remove the 3 from 53 leaving you with a 5; you then type the 6 to make 56:

• The a b/c key: This key is located at the beginning of the third row of gray keys above the number keys. This key allows you to switch back and forth between fractions and decimals. This then is one way to change a fraction into a decimal.
• • For example: you want to change 7/8 into a decimal: Press the 7 key, then the a b/c key, and then the 8 key. You will see something like this: 7 ⌋ 8 This stands for the fraction 7/8. Then to change the fraction to a decimal, press the equal sign key and then the a b/c key; then you will see 0.875 in the display. If you press the a b/c key again, the display will change back to 7 ⌋ 8.
  • Try this: 7,  a b/c,  8,  =,  a b/c This will give us 0.875 as an answer. We have changed 7/8 into its decimal equivalent.
  • Change these fractions into decimals using the above method:

a.)  3/4 = 0.75     b.)  1/2 = 0.5     c.)  1/8 = 0.125     d.)  3/16 = 0.1875

• • ANSWERS – keep these? e) 1/4 = 0.25f) 3/8 = 0.375g) 7/16 = .4375

    h) 3/32 = 0.09375i) 15/16 = 0.9375j) 33/64 = 0.515625

    k) 21/32 = 0.65625I) 57/64 = 0.890625

    m) 5/8 = 0.625n) 17/32 = 0.53125

• The a b/c key (continued): It is also possible to change a mixed number to a decimal expression by the use of the a b/c key, e.g. 2 3/4 = 2.75. A mixed number is entered into the computer in this manner: press 2, then a b/c, then 3, then a b/c, then 4, then =, then a b/c. Before you press the final a b/c, the display will show: 2 ⌋ 3 ⌋ 4.
  • Answers — keep??

a) 45 7/8 = 45.875b) 8 43/64 = 8.671875

c) 10 3/64 = 10.046875d) 3 19/32 = 3.59375

e)264 3/4 = 264.75f)1389.546875

g) 3 3/8 = 3.375h) 2345 7/32 = 2345.21875

• Another method for changing fractions into decimals: Another way to change any fraction into a decimal is to divide the numerator by the denominator: e.g., 3/4 can be changed by dividing 3 by 4: Press AC to clear the display, then press 3, then press , then press 4, then press =, and you will see 0.75 in the display.
  • Note: You may have noticed that in our practice of changing fractions, we have used only halves, fourths, eighths, sixteenths, thirty­ seconds, and sixty-fourths. This was done, because these are the fraction most often used by the machinist in working with dimensions given in fractions of the U.S. Customary inch. A machinist would want to be able to change the fractional dimen­sions of a machine part to their decimal equivalents. Such decimal meas­urements could then be easily entered into the computers of numerical control machines. A numerical control machine is any machine tool which can be controlled by computer programming to perform precise jobs, like cutting, drilling, etc.
  • Answers to practice at top of this page: — KEEP?

a) 5/16 = 0.3125b) 27/64 = 0.421875 c) 9/32 = 0.28125d) 9/64 = 0.140625 e)63/64 = 0.984375f) 3/4 = 0.75

g) 1/32 = 0.03125h) 1/64 = 0.015625

i) 1/2 = 0.5j) 19/64 = 0.296825