Texas Instruments TI-15 User manual

TI-15 ExplorerTM Support Book

Chapter Name

Page

1. Introduction to the display

I. Display, scrolling up and

down, order of operations

and using brackets.

II. Clearing and correcting

2. Mode menus

I. Calculator

II. Problem solving

III. Fraction

3. Basic operations including

exponents (powers) and square root

4. Whole numbers and decimals

5. Fractions

6. Percent

7. Constant operations

8. Problem solving in Auto mode

9. Problem solving in Manual mode

10. Place value

11. Memory

12. Error messages

13. Display indicators

14. Copyright information

TI-15 Explorer ™ is a trademark of Texas Instruments

1. Introduction to the Display

a. Using your thumbs, press and hold down both and at the same time, then

release both keys at the same time. MEM CLEARED is displayed.

This RESETS the calculator to its default settings.

b. Press . The blinking triangle cursor is displayed. The calculator is ready to use.

c. Key in . 10 x 10 = 100 is displayed.

You can see both the problem and the answer at the same time.

d. Now key in  (10 x 9 = 90 is displayed), and  (10 x 8 = 80

is displayed). The “up arrow” indicator in the calculator window lets you know that

you can scroll up.

e. and move the cursor left and right, and move the cursor

up and down through previous entries.

A small arrow will appear at the left hand side of the screen when

this is possible.

f. is used to open an expression with brackets,

and must be used to close before selecting ,

otherwise Syn error is displayed.

Operations in brackets are always performed first.

You can review entries and look for patterns.

g. In terms of priority, the calculator will perform in the following order:

Brackets and 

Fractions 

Exponents and square roots and 

Negative 

Multiply and divide and 

Add and subtract and 

Convert to fraction or decimal 

Complete 

NB Since the calculator will always do what is in brackets first, the use of

brackets can change the required order and so change the answer or result.

h. Clearing and correcting

turns the calculator on and off, but will not clear settings or previous

entries.

clears only the last entry and any error statements. It does not affect mode

settings, memory or constants.

will clear the last digit entered so that you do not need to re-enter an entire

number.

Pressing and simultaneously resets settings to defaults and clears

memory and constants.

2. Mode menus

See worksheets for further explanations and uses.

a. Calculator mode

[Press and , and to set.]

I. Press and choose style for division

II. Press , then and to select .

When +1 is underlined and selected, the Constant operation is displayed.

When ? is underlined the operation is not shown.

See worksheets

b. Problem solving mode

Press to enter problem solving and 

with and and to set.

To exit problem solving press and the

small icon will disappear from the screen.

In MAN (manual mode) you can enter

your own problem –eg ? x ? = 36,

and the calculator shows that this has

9 solutions –it only counts positive whole

numbers, and 9 x 4 is different from 4 x 9.

Also in MAN mode,

the place value menu is available. See section 10 for further information.

Inequalities and equalities can be tested. Press once for LESS THAN,

and  for GREATER THAN. The calculator will indicate whether a

statement is correct (YES) or incorrect (NO).

c. Fractions menu

Press and to choose then to set. See fractions section below.

3. Basic operations, including exponent (powers) and square roots

a. These are the usual operations with , , , and , except

that the result of a division depends on which mode is set for

it.

This screen is accessed by pressing and using the side

arrows to choose whether the answer should be a decimal or

a fraction. Press to set.

If you attempt to divide by 0, an error message is displayed.

Negative numbers can be used by entering the symbol before the integer.

b. divides a whole number by a whole number and

displays the result as a quotient and remainder.

The divide symbol is slightly larger than the standard one

on the screen.

If this result is used in the next calculation, the remainder

is dropped.

c. lets you calculate a number to a given power.

It allows the use of negative exponents (see worksheets)

and lets numbers be entered in scientific notation.

eg entering  gives 8 ie (2 x 2 x2),

and entering   gives 0.125 which when

changed to a fraction becomes 1/8 after simplification.

d. calculates the square root of positive values

including fractions but the answer will be a decimal

which may or may not be able to change to a fraction.

NB brackets must be closed.

e. Numbers can be entered in scientific notation using the key.

eg 2.3 x 10^2 + 1.4 x 10^3 = 1630

2.3 x 10^8 + 1.4 x 10^10 = 1.423 x 10^10

When the number of zeros goes beyond the screen, the number will appear in

scientific notation.

4. Whole numbers and decimals

a. The key sets the number of decimal places

together with the appropriate RED Place Value

key from the left hand side of the calculator.

The rounded result is displayed but the original

number is retained in the memory.

must be pressed each time the number is

to be rounded off.

removes the fixed decimal setting.

needs to be pressed before is effected.

It can be applied to and individual number or

before is pressed to complete a calculation.

eg Entering will do the

calculation but return an answer rounded to 1 dec place.

Pressing gives the full answer 167.832

While the symbol is visible numbers entered will

be displayed to the pre-set number of decimal places.

eg if  has been used, then until it is cleared, any further calculations will answer

to the nearest whole number, although the actual answer will still be stored.

b. When is used to change a fraction to a

decimal and back to a fraction, sometimes the

fraction needs to be simplified to get back to

the original.

eg 5/8 changes to 0.625 then back to 625/1000.

NB when a fraction can be simplified the symbols

N

will be displayed at the top of the screen

until no further simplification is possible.

This is changed back to 5/8 using the key.

c. Three Results of Division

There are three different ways that a division can be displayed on the screen.

Decimal answer (i)

Quotient and remainder answer (ii)

Fraction answer (iii)

i. Decimal answer Key in 

5.429 

is displayed.

This shows the standard decimal answer to a division problem.

ii. Now key in This time

1429 r

is displayed.

This shows the quotient and remainder answer to a division problem.

iii.. Now set the calculator to give a fraction answer to a division problem.

Press . The selection . n/d is displayed.

This lets you select decimal or fraction answers to division problems.

Press the right arrow key to underline n/d. Press to confirm your selection.

The n/d indicator in the screen lets you know that the calculator will now give fraction

answers to division problems.

Press to exit the menu. Notice that n/d is still displayed.

Now key in .

429 

(a stacked fraction) is displayed.

This shows a fraction answer to a division problem. Notice also that the fraction result will not

be in simplest form necessarily. See later for how to simplify.

Press the up arrow key once to scroll up. Press again. The calculations you entered

previously are displayed. Press the Down arrow . Press the Down arrow again.

You can review the three different results of the division problem and explore with your

students why the same problem gets three different-looking answers.

Students will come to understand that all three answers are the same and make the

connection between decimals, quotients and remainders, and fractions.

5. Fractions

a. displays a menu from which

the way a fraction is shown is set

- Un/d displays a mixed number and

- n/d displays a single fraction (improper fraction) result.

and whether any given fraction is unsimplified (Man) with

N

showing at the

top, or in simplest terms with Auto

This lets you select to display fraction results as mixed numbers or improper

fractions.

Press the left and right arrow keys and to move the underline. To select

mixed numbers, underline U n/d and press . To select improper fractions,

underline n/d and press .

Press the down arrow



. The selection MAN AUTO is displayed.

This lets you select to manually simplify fractions (using the key), or have the

calculator automatically simplify fractions.

Press and to move the underline.

Press to exit the Fraction Menu.

b. A mixed number is entered using the button after the whole number part,

after the numerator and after the denominator, followed by , or the next part

of a calculation.

c. changes a mixed number to an improper fraction and vice versa.

d. When the calculator is in Auto mode, and

N

is visible, pressing simplifies

the fraction to lowest terms in one step.

e. When the calculator is in Man mode, and

N

is visible,

pressing simplifies the fraction to lowest terms in steps where the factor or

divisor to be used can either be entered by the user or the calculator chooses the

factor.

Pressing shows the factor that was used, and pressing it again displays the

simplified fraction. This is repeated until the

N

is no longer on the screen.

The calculator uses the lowest prime number available as a factor first, then moves

to the next prime factor until the fraction is fully simplified.

f. For calculations, the denominator can be from 1 to 1000. For conversions to decimals,

the denominator can be from 1 to 100,000,000.

g. Stacked fractions, Entering mixed numbers, numerators, and denominators

Key in .

8

is displayed.

You can enter either the numerator or denominator first. Fractions are stacked. You

can see the whole problem and the answer at the same time.

h. Converting mixed numbers to improper fractions

Press to convert the mixed number to an improper fraction.

is displayed. Press again to convert back to the mixed number.

displayed.

i. Converting fractions to decimals and vice versa

Press to convert the fraction to a decimal.

9.375 is displayed. Press again to convert back to the fraction.

This time

1000

375

is displayed.

The calculator uses the decimal value to create the fraction. The N/D n/d indicator at

the top of the screen lets you know that the fraction can be simplified further.

j. Simplify by a factor you choose.

Press .

is displayed. Press to see the factor used to simplify the fraction.

25 is displayed. The numerator and denominator were each divided by 25.

Press again to return to the fraction.

is displayed again.

The N/Dn/d indicator lets you know the fraction can still be simplified further.

k. Simplify by a factor the calculator chooses.

Press .

is displayed.

Press to see the factor used to simplify the fraction. 5 is displayed. Press

again to return to the fraction.

is displayed again.

The N/Dn/d indicator is no longer displayed. This means that the fraction cannot be

simplified any further.

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