Calculator giving incorrect answers

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Guest

I am new to XP Prof, and just want to know if Microsoft knows that the
calculator (Start, Programs, Accessories, Calculator) does not calculate
correctly when dividing by a percentage.

The problem is (example): 80 divided by 80% = 100. But when you put this in
the calculator is comes up with 64 (which is actually 80 multiplied by 80%
(or .8). I tried other numbers too. (70 / 50% = 140, but the Calculator comes
up with 35 - which is 70 multiplied by 50%.) It only seems to happen when
using the percent sign, not when entering as a decimal. Entering 80 / .8
gives the correct answer of 100, but entering 80 / 80 % gives 64.

I looked around different groups, etc, but I'm fairly new at this, and
frustrated trying to find this out if there's a fix out there. Does anyone
know? Thank you.
 
Actually, the calculator works great - all 128 bits of
precision.

Hint: The "divide" key is the "/" key.
I looked around different groups, etc, but I'm fairly new at this,
Click to expand...

I would've never guessed.
 
You need to give him the benefit of doubt considering the fact that it
is xmas period and he must have had one or two glasses of undiluted
liquid!
 
80 percent is .80 - not 80%

Try it!

--


Regards,

Richard Urban
Microsoft MVP Windows Shell/User

Quote from George Ankner:
If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!
 
Actually 80% of 80 IS 64. The calculator works as designed. The system
ignores the "divide" because you pressed the percent. You could press
the + or the * or the - between the entering the numbers and you will
get the same thing.
 
I am new to XP Prof, and just want to know if Microsoft knows that the
calculator (Start, Programs, Accessories, Calculator) does not calculate
correctly when dividing by a percentage.

The problem is (example): 80 divided by 80% = 100. But when you put this in
the calculator is comes up with 64 (which is actually 80 multiplied by 80%
(or .8). I tried other numbers too. (70 / 50% = 140, but the Calculator comes
up with 35 - which is 70 multiplied by 50%.) It only seems to happen when
using the percent sign, not when entering as a decimal. Entering 80 / .8
gives the correct answer of 100, but entering 80 / 80 % gives 64.

I looked around different groups, etc, but I'm fairly new at this, and
frustrated trying to find this out if there's a fix out there. Does anyone
know? Thank you.
Click to expand...

You are making a common mistake. The percentage function in a
calculator is used to find the specified percentage of the number
entered. That is the defenition of a percentage. In other words the
percent key will always do what you are seeing and is actually doing
what it is supposed to do.

Try it on any calculator and you will get the same result.

If you want to divide by a percentage then you have to use the decimal
equivalent.
 
LH said:
I am new to XP Prof, and just want to know if Microsoft knows that the
calculator (Start, Programs, Accessories, Calculator) does not calculate
correctly when dividing by a percentage.

The problem is (example): 80 divided by 80% = 100. But when you put this
in
the calculator is comes up with 64 (which is actually 80 multiplied by 80%
(or .8). I tried other numbers too. (70 / 50% = 140, but the Calculator
comes
up with 35 - which is 70 multiplied by 50%.) It only seems to happen when
using the percent sign, not when entering as a decimal. Entering 80 / .8
gives the correct answer of 100, but entering 80 / 80 % gives 64.

I looked around different groups, etc, but I'm fairly new at this, and
frustrated trying to find this out if there's a fix out there. Does anyone
know? Thank you.
Click to expand...

It's a question of how you are defining the operation.

The "%" key on a calculator was designed to allow such operations as

80 + 10 % = 88 (ie. 80 plus (10 % OF 80))
80 - 10 % = 72 (ie. 80 minus (10 % OF 80))

so, by implication,
80 * 10 % = 640 (ie. 80 times (10 % OF 80))
80 / 10 % = 10 (ie. 80 divided by (10 % OF 80))

which is precisely what you get if you press the "=" after the "%." When you
press the "%", the display shows the result of calculating using (the second
entry) percent of (the first entry)
The problem is (example): 80 divided by 80% = 100. But when you put this
in
the calculator is comes up with 64
Click to expand...

80 / 80 %
calculator shows 80% of 80 (64)
PRESS = to show 1.25 [80/(80*(80/100))]

.... (70 / 50% = 140, but the Calculator comes
up with 35 - which is 70 multiplied by 50%.) It only seems to happen when
Click to expand...

70 / 50 %
calculator shows 50% of 70 (35)
PRESS = to show 2 [70/(70*(50/100))]

HTH

....Bill
 
LH said:
I am new to XP Prof, and just want to know if Microsoft knows that the
calculator (Start, Programs, Accessories, Calculator) does not
calculate correctly when dividing by a percentage.

The problem is (example): 80 divided by 80% = 100. But when you put
this in the calculator is comes up with 64 (which is actually 80
multiplied by 80% (or .8).
Click to expand...


There's really no such defined operation as dividing by a percentage. You
are presumably clicking on the following buttons 8 0 / 8 0 %. When the
calculator sees you enter that % sign it simply ignores the meaningless /
sign, and calculates that percentage--80% of 80, which is 64.

It's not multiplying by 80% either; that's also an undefined operation; it's
simply calculating the percentage 80% of 80. You can divide or multiply by a
number, such as .80, but not by a percentage.
 
If you do the calculation on a real desk calculator, or even on the
calculator on your cell phone, it comes up correctly. ( 80 / 80% comes up
with 100) I just wondered why it didn't work the same as all the desk
calculators I have used for the last twenty years.

We use this function all the time where I work with medical insurance
payments.
The payment comes in and they've taken a deductible, but don't tell us how
much. So if I get a payment for $64.00, and I know that the insurance policy
pays 80%, I take 64.00 / 80% to get $80.00. Our charge was $100, so I know by
deduction that they took $20.00 towards the patient's deductible.

Another reason to use this type of calculation: suppose I contribute $1,200
to a company stock purchase plan over the last year. I'm eligible to buy it
at 85% of the price. How much can my $1,200 buy? $1,200 / 85% =approx $1,412.
worth of stock. I guess I'll just continue to use my desk calculator.

Thanks for all the replies.
 
LH said:
If you do the calculation on a real desk calculator, or even on the
calculator on your cell phone, it comes up correctly. ( 80 / 80%
comes up with 100)
Click to expand...


You're calling that "correctly," but as I pointed out, there's nothing
"correct" about it. Dividing by a percentage is not an arithmetic operation,
and the result is undefined. You can divide by numbers, but not percentages.
This is akin to dividing 80 oranges by 80 miles per hour. The answer is not
100. There is no *correct* answer to such an operation.

I just wondered why it didn't work the same as all
the desk calculators I have used for the last twenty years.
Click to expand...


I don't know what desk calculators you've used, or what answers they
produce, but it doesn't matter. It's still an undefined operation. It
probably would be better if it gave you an error message, but neither 100
nor 64 is *correct*.

We use this function all the time where I work with medical insurance
payments.
The payment comes in and they've taken a deductible, but don't tell
us how much. So if I get a payment for $64.00, and I know that the
insurance policy pays 80%, I take 64.00 / 80% to get $80.00.
Click to expand...


You're doing it wrong. You should be dividing 64 by .80 (a number, not a
percentage). That will always give you the correct answer. If your
calculator produces the correct result when you perform an undefined
operation, consider yourself lucky.
 
You're calling that "correctly," but as I pointed out, there's nothing
"correct" about it. Dividing by a percentage is not an arithmetic operation,
and the result is undefined. You can divide by numbers, but not percentages.
This is akin to dividing 80 oranges by 80 miles per hour. The answer is not
100. There is no *correct* answer to such an operation.




I don't know what desk calculators you've used, or what answers they
produce, but it doesn't matter. It's still an undefined operation. It
probably would be better if it gave you an error message, but neither 100
nor 64 is *correct*.




You're doing it wrong. You should be dividing 64 by .80 (a number, not a
percentage). That will always give you the correct answer. If your
calculator produces the correct result when you perform an undefined
operation, consider yourself lucky.
Click to expand...

The desk calculator is smarter than the m$ product since it knows about
the % sign & has the intelligence to change it to a decimal prior to
doing the calculation.

It looks the m$ product isn't intellegent enough to understand percentages
or its usage.
 
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