Approximating the Solution

[frog1944]

Hi,

For the 2012 HSC MX2 Question 13 a) iii), they ask "How far does the object sink in the first 4 seconds?", I evaluated it in exact form however (which was painful to manipulate and simplify it down), though their worked solutions just kind of plugged it in and then approximated. How do I know when I can do this? Are you allowed to do this?

Thanks

(Page 13 is the worked solution to the problem; http://educationstandards.nsw.edu.au/wps/wcm/connect/ca895cec-8b34-45c8-9c1a-9328cf622be1/maths-ext2-hsc-sa-2012.pdf?MOD=AJPERES&CACHEID=ROOTWORKSPACE-ca895cec-8b34-45c8-9c1a-9328cf622be1-lG9Dwmb)

[pikachu975]

I think you can do it if it doesn't say "exact form" but you need to use a bit of common sense when deciding.

[RuiAce]

For a 2-marker, trying to simplify that expression sounds like a waste of time to me.

The mark allocation was most likely 1 mark for you subbing in t=4, and then the next mark for just correctly subbing into the equation for x and obtaining something valid. Once you were at the nastily long log, you already had an exact expression, and there's no indication that suggests you should simplify that exact expression further.

[frog1944]

Ok, thanks