Logs without calculator?

[closertofine]

I know that no calculators are allowed on the MCAT, but now I'm wondering how we're supposed to do logs without them. Maybe I'm just out of the loop, but I've never done anything but simple logs by hand.

Also, have any of you had a little difficulty with the basic calculations on the physical science section? I probably sound stupid, but it's been a long time since I actually did long division by hand! And I feel like there must be some trick to get it done faster, but I have missed out...


Thanks,

Karen

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[mpp]

I don't know why you would need to do logs on the MCAT but logs can be fairly straightforward if you know the basics.

Log 1 = 0
Log 10 = 1
Log 100 = 2
Log 1000 = 3

That is, just count the zeros. If you have a number 57, then the log 57 is greater than 1 but less than 2.

Numbers between 0 and 1 have negative logs.

Log 0.1 = -1
Log 0.01 = -2
Log 0.001 = -3

Just count the number of digits between the decimal point and the last number on the right. The log 0.46 is somewhere between -1 and -2.

For natural log (ln) it is the same thing except you use powers of e instead of powers of 10 (e=2.718...). So

Ln 2.718 = 1
Ln 7.389 or Ln 2.718*2.718 = 2
Ln 20 or Ln 2.718*2.718*2.718 = 3
Ln 54.5 = 4
etc.

So Ln 16 is between 2 and 3.

As far as doing quick math on the MCAT, just learn how to estimate quickly. This is usually good enough for the answers. But practice long division/multiplication just in case.

Another good number to know for use in trigonometry (not that there is much of this on the MCAT) but square root of two is about 1.4.

 

[fantasie]

Just count the number of digits between the decimal point and the last number on the right. The log 0.46 is somewhere between -1 and -2.

I think you meant between 0 and -1 cuz the log of .46 is -.327

 

[circulus vitios]

I think you meant between 0 and -1 cuz the log of .46 is -.327

He can finally stop holding his breath after these past 10 years, hoping that no one would correct his mistake.