An interesting use of Op1 with fractions:1. Ask students to “count on” orally from 0 by 2 to 20, then by 5 to say 30, to ensure

that they understand “counting on”. This can be demonstrated on the calculator by setting Op1 to +2 (or +5) and locking it in.

i. Press � to open the operation. Press Tlto enter “add 5” as the constant.

Press � to store and close the operation and lock it in. + 5 is displayed.

The Op1 indicator at the top of the screen lets you know that the operation is

stored.

ii. Press q ® to “initialize” the constant with a starting value of 0.

0 = 0 is displayed. You can choose any starting number.

iii. Press � to start the constant operation.

The “expression” 0 + 5 is displayed on the top line.

The 1 on the bottom line is the number of times the

operation has been performed. The 5 on the bottom line is the result.

iv. To continue the constant operation, press � repeatedly.

You can press the Up and Down arrows to scroll up and down to review the

series of constant operations but they cannot be changed.

2. Ask the students to count on from 0 by halves. ie 0, 12 , 1, 1

12 , 2, ........

Some students may say “two halves” rather than 1.

This needs to be carefully discussed and agreement reached about whether the

fractions are simplified or left as improper fractions.

This can also be demonstrated on the calculator setting Op1 as +12 and locking it

in. BUT, the calculator allows you to choose the style of answer given – ie an

unsimplified fraction or simplified, and when the answer is bigger than 1, a mixed

number or an improper fraction.

NB that when Op1 is a fraction, the display just gives the answer and the

number of times it has been used. Scrolling up a line shows the expression.

Using OP1 with fractions on the TI 15 1

3. Setting the TI-15 for fractions with Op1 set as + 12:

a. For unsimplified and improper fractions, press the menu.

U n/d n/d appears on the screen.

Move the cursor so that n/d is underlined and press ENTER.

This will ensure unsimplified improper fractions are

maintained. (NB scrolling down once shows that the

calculato in MANual mode too rather than AUTO.)

This is the screen after Op1 is pressed 4 times:

b. For automatically simplified IMPROPER fraction keep n/d set but

underline AUTO to set that action.

This is the screen after Op1 is pressed 5 times:

c. For automatically simplified mixed number fractions U n/d must be set

in the FRAC menu, as well as underline AUTO to set that action.

This is the screen after Op1 is pressed 5 times:

Using OP1 with fractions on the TI 15 2

4. Now ask the students to count on with 16 . This might be best done by writing

down answers rather than just saying them, as a variety of answers will result: eg

a. 16 , 26 , 36 , 46 , etc., simply adding 1 to the numerator.

b. 16 , 13 , 12 ,

23 ,

56 , 1 , 76 etc., simplifying as

16 is added and recognising

whole numbers but leaving improper fractions.

c. 16 , 13 , 12 ,

23 ,

56 , 1 , 1 16 etc., simplifying as

16 is added and recognising

whole numbers and changing improper fractions to mixed numbers.

5. This can be illustrated on the calculator with students working in pairs – one with the calculator set at n/d and MAN from the FRAC menu, and the other set at Un/d and AUTO B from the FRAC menu. Encourage students to compare and record their results eg in a table.

How many OP1 Result without any simplification

Result with AUTO simplification

eg 0 + 16 , 8 times86

1 13

This can also be illustrated using the MATHCULATOR software by opening the program twice on the screen and setting each calculator mode appropriately.

Students should be encouraged to add on verbally using fractions that give opportunities for mental simplification. Working in pairs one might use the calculator while the other does the verbal and vice versa.

Using OP1 with fractions on the TI 15 3