Copy and Paste on CAS calculator

[arie12345]

Hi guys,

Whilst using finance solver to work out questions that require multiple steps, when transferring values from PV to FV or FV to PV and stuff like that should I use the copy and paste funciton of the calculator or just use the rounded answer to two decimal places? My teacher says round the answer before transferring it, however, in methods I know that the exact answer is needed when calculating results.

Thanks in advance

[Lear]

Depends on the situation. If you are working across multiple sub questions and a an earlier sub questions asks your to round, you must use this rounded value in subsequent calculations and questions. However, if it is simply one question where you are required to do transfers such as often happens when there are changes enacted on a loan mid way, you should copy paste the values in full form. Remember to change signs.

[arie12345]

Depends on the situation. If you are working across multiple sub questions and a an earlier sub questions asks your to round, you must use this rounded value in subsequent calculations and questions. However, if it is simply one question where you are required to do transfers such as often happens when there are changes enacted on a loan mid way, you should copy paste the values in full form. Remember to change signs.

Okay, should I ask my Further Teacher to double check with VCAA to make sure she isn't correct? Because she has told the enitre class not to copy and paste in the one question, and to use rounded answers in finance solver. The result is of course different by a few decimal places.

[Lear]

Okay, should I ask my Further Teacher to double check with VCAA to make sure she isn't correct? Because she has told the enitre class not to copy and paste in the one question, and to use rounded answers in finance solver. The result is of course different by a few decimal places.

If it is a single question for example 2017 VCAA Further Maths finance question 7B, you should not round within intermediate steps. Your teacher is misinformed. All they need to do is go have a look at the examiner's report for last year and note that they did not round to two decimal places between the two calculations. This is also mentioned in the general comments section as seen below.

Students should also take care to avoid premature rounding. They should use all the decimal
places in their calculator for intermediate steps and then only round the final answer to the required
accuracy level

Here's another reference from the 2014 Further maths examiners report.

The price of an item or account should be written correct to the nearest cent if there are no rounding instructions
included in the question. In general, when the answer for a previous question is expected to be rounded, then students
should use that rounded final answer for the consequential question. Intermediate values should not be rounded within a
question. Intermediate values should be retained and the final answer should only be rounded as required.

[S_R_K]

If you are using the TI, then another good way to handle calculations requiring multiple steps of finance solver is to use the stored variables "tvm.pv", "tvm.pmt", etc. These will also give you maximum accuracy.

For instance, for a changing conditions question where, say, the monthly payment or interest rate changes partway through the loan, you can do the following:

1. Calculate the FV for the first part of the loan, as you normally would.
2. Type in "-tvm.fv" as your new PV for the second part of the loan, then change other fields as required.

You can, of course, use a similar technique for calculating the total interest or total cost of a loan to maximum accuracy, by using N * -tvm.pmt.