1. The “Math Class” Mistake (Chain Mode)
The Problem:
You type 1 + 2 * 3 into your calculator.
- Your brain says: 7 (because multiplication happens before addition).
- Your calculator says: 9.
Why?
By default, this calculator is in CHN (Chain) mode. It calculates numbers in the exact order you type them (1+2=3, then 3*3=9). It ignores “Order of Operations” (PEMDAS). This is the #1 reason students fail their first quiz.
The Fix:
Change your settings to AOS (Algebraic Operating System) immediately.
- Press 2nd then FORMAT.
- Scroll down until you see
CHN. - Press 2nd then SET to change it to
AOS. - Never touch it again.
2. The “Ghost Data” Mistake (Memory)
The Problem:
You finish Question 1 about a car loan. You turn your calculator OFF and then ON again to start Question 2 about a mortgage.
Suddenly, your answer for Question 2 is totally weird.
Why?
Turning the calculator off does not delete the data. It has “Constant Memory.” The interest rate and loan term from the car loan are still lurking in the background, messing up your mortgage calculation.
The Fix:
Stop trusting the ON/OFF button. You must manually wipe the memory before every single problem.
- For loans/interest: Press 2nd + CLR TVM.
- For cash flows: Press 2nd + CLR WORK.
3. The “Decimal Point” Mistake (Interest Rates)
The Problem:
The problem says the interest rate is 5%. You type 0.05 into the I/Y key.
Your monthly payment comes out to be like $2.00.
Why?
In math class, you learned that $5\% = 0.05$.
But the BA II Plus is programmed for lazy bankers. It assumes the number you type is already a percentage. If you type 0.05, the calculator thinks the interest rate is 0.05% (which is basically zero).
The Fix:
If the rate is 5%, just type 5.
If the rate is 6.5%, type 6.5.
4. The “Money In, Money Out” Mistake (Sign Convention)
The Problem:
You enter a Loan Amount ($20,000) as a positive number.
You enter the Monthly Payment ($400) as a positive number.
You press compute… and the screen screams ERROR 5.
Why?
The calculator follows the Cash Flow Sign Convention. It needs to know which way the money is moving. You cannot receive a loan (+) and receive a payment (+) at the same time. One has to leave your pocket.
The Fix:
- Cash Inflow (Loan, Withdrawal): Positive (+).
- Cash Outflow (Deposit, Payment, Investment): Negative (-).
- Tip: Use the
+/-key (next to the equals sign), not the minus key!
5. The “Fake Clear” Mistake (CE/C)
The Problem:
You make a mistake, so you mash the CE/C button a bunch of times until the screen says 0. You think you are safe. You are not.
Why?
CE/C stands for “Clear Entry” or “Clear Screen.” It is just a Backspace button. It clears the screen, but it does not clear the variables stored deep in the memory (like N, I/Y, or PV). They are still there, waiting to ruin your next calculation.
The Fix:
Use the “Nuclear Option” keys mentioned in Point #2.
- CE/C = “I made a typo.”
- 2nd + CLR TVM = “I am starting a new problem.”