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# Editing Keys on the Calculator

Reference > Mathematics > TI-30X II

Suppose you wanted to find the sum of 152 and 32, but when you typed this into your calculator you began by typing 1522 instead of 152. Do you need to clear the screen and start again? No! You have a very handy key on your calculator called the DELkey. DEL means delete. Try this: type 1522, and then press the DEL key at the top of the calculator. What happens?

What you should see is that the second 2 disappears, leaving you with just 152, which is what you wanted.

Suppose you wanted to type my favorite number (142857) but you accidentally typed 143857. Is there any way to fix that? Yes! Find the arrow that points left (it's in the upper right corner of the calculator), and press it 4 times. Each time you press it, the cursor (the little black box) moves to the left, until it is positioned over the number 3. Now if you press the number 2, that will replace the 3. Now you can use the right arrow key to move back to the end of the number and continue on.

Suppose you typed the number 14857 instead of 142857. This is a little different. Why? Because instead of typing a WRONG number, you left a number out. Try this: press the left arrow 3 times, until the cursor is over the 8. Now press the following keys: 2nd and DEL. If you're paying attention, you'll notice that the second function forDEL is INS. This stands for insert. Notice that when you press INS, the cursor goes from being a box to a blinking underline. When you see this, it means that the next key you press will be inserted instead of overwriting what is in the display. So press the number 2 now, and you'll see the 8, 5, and 7 all shifted to the right to make room for the number 2.

That's all well and good, but sometimes you don't realize you've made a mistake until after you've typed in the entire line and pressed "=". After all, a good mathematician (or scientist) looks at the answer to see if it makes sense, and if you typed something wrong, your answer might not make sense.

Suppose you intended to type 142857 x 7, but instead you typed 142856 x 7, and then you pressed equals. Once you did that, you realized that you'd made a mistake. Is there any way to fix the mistake, without retyping the whole thing? Yes there is!

Press the up arrow (in the upper right corner of the calculator), and you'll see that your line with the mistake reappears. Now you can use the left/right arrows along with INS and DEL to fix what you've typed. Then press equals to get your new answer.

## Questions

1.
If you typed 134, but intended to type 14, what keys would you press to fix the mistake?
2.
If you typed 14287, but meant to type 142857, what keys would you press to fix the mistake?
3.
If you typed 5432, but intended to type 5442, what keys would you press to fix the mistake?
4.
If you typed 32 + 24, but meant to type 32 - 24, what keys would you press to fix the mistake?
5.
If you typed 5 + 4 =, then realized you should have typed 5 - 4 =, what keys would you press to fix the mistake?
6.
If you typed 142+32 =, then realized you should have typed 14-32=, what keys would you press to fix the mistake?
7.
If you typed 45-11=, then realized you should have typed 452-311, what keys would you press to fix the mistake?
8.
If you typed 3-4+2 =, then realized you should have typed 3-(4+2), what keys would you press to fix the mistake?
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