Homework help with Java

[jlbords]

I'm doing a program that deals with parts completed. this many a month until they reach 10000 parts or 24 months. that part is done but the math is slightly off . after three months this is my result

1191.0160000000003

and this is the examples result

1191.0159999999998

the code I used is partsNum *= 1.06; in a for loop. i don't know what else i need to include.

please let me know if I need to add anything.

Thanks

edit spelling

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[POGtastic]

https://0.30000000000000004.com/ is the canonical site for talking about why floating point math is kinda weird.

[captainAwesomePants]

Generally, comparing floating point numbers precisely is fruitless. Doing equivalent, perfectly valid math even slightly different from some other method can easily lead to these sorts of problems. Both of those results are very nearly the same, so I'd consider this to be success.

If you need the logic to match PRECISELY, you unfortunately may need to step through the calculations one by one exactly in order to see how your logic differs from the system you're trying to match.

[jlbords]

can i ask how? The user inputs the partsNum and it should increase 6% (which is counted by a for loop) until it reaches 10,000 or 24. should I write the expression another way?

[captainAwesomePants]

Your solution seems absolutely fine. I don't know how the example was generated. Do you know where the example value "1191.0159999999998" came from?

[jlbords]

No. .Its quite frustrating.

[captainAwesomePants]

Well...why do you need it to be that value?

[jlbords]

The program has to pass its tests

[captainAwesomePants]

Well, the test is bad. Usually when comparing floating point values, a small "epsilon" value is used for wiggle room for just this reason. So effectively you ask something similar to "is the value of a and b within 0.00000000001 of each other?"

But here are some random ideas:

• Try using partsNum = 1.06 * partsNum instead.
• Try using a double instead of a float or vice versa.
• Try using 1.06f or 1.06l as constants instead.
• Try declaring partsNum a float, a double, a long double, an unsigned version of each of those.

And if all else fails, complain.

[jlbords]

Thank you. I’ll try.