# MCAT Mathematical tricks

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1. ([Any number]E-n )*10 =

ex.
(2.7E-5)*10 =
([Any number]E-n )*10 = [AnyNumber]E-(n-1)

• ex.
• (2.7E-5)*10 = 2.7E-4

-Since multiplying the number by ten will make it bigger number, then it makes sense that the exponent should become less negative, in order for the number to get bigger, or in other words, clower to a whole number.
2. These cards are being made on 7/21/2011, and I'll continue updating them as I study, so if you are using them between now and mid August, you should constantly check for updates. - Let's not let little mistakes slow us or claim points on MCAT/DAT, or whatever you are using them for
:P
3. ([Any number]E-n )/10 =

ex.(2.7E-5)/10 =
([Any number]E-n )/10 = [AnyNumber]E-(n+1)

ex. (2.7E-5)/10 = 2.7E-6

• Since dividing the number by ten will make it smaller number, then it makes
• sense that the exponent should become more negative, in order for the
• number to get smaller. In other words the exponent should cause the number to shift further away from being a whole number.
4. 27E-3 = 2.7E?
27E-3 = 2.7E-2

So, what you have to do is divide the number 27 by 10, and multiply the exponent by 10.

when you multiply a negative exponent by 10, this will make the number bigger, thus the exponent should become less negative, thus (#E-n)*10 = #E-(n-1)
5. 2.7E-3 = 27E?
2.7E-3 = 27E-4

Multiply 2.7 by 10, and divide exponent by ten. since the exponent is dividded, the numbeer will get smaller, thus it makes sense that the expoenent should get more negative.
6. 27E3 = 2.7E?
2.7E4

Divide 27 by 10, and muliply exponent by 10
7. 2.7E3 = 27E2
Multiply 2.7 by 10, and divide exponent by 10
8. sin(30)
0.5
9. sin(45)
0.7
10. sin(60)
0.85
11. cos(30)
0.85
12. cos(45)
0.7
13. cos(60)
0.5
14. to convert areas from cm2 to m2
• Multiply by 1E-4
• (divide by ten thousand)
15. to convert volume from cm3 to m3
• Multiply by 1E-6
• (divide by a million)
16. to convert length from cm to m
• Multiply by 1E-2
• (divide by a hundred)
17. log 2 =
0.3
18. log 3 =
0.5
19. log 5
0.7
20. ln 2 =
0.7
21. ln 3
1.1
22. ln 5
1.6
23. log 10 =
1
24. log 100 =
2
25. log 1000
3
26. log 10000
4
27. log 1E^n =
n
28. log (y/z) =
log (y) - log (z)
29. log (xy) =
log (x) + log (y)
30. log(anynumber x 10n) =
~ > n
31. log (anynumber x 10-n) =
~ > - n
32. log 7
0.85
33. to get mL to L do what?
Mult by E-3. (effectively dividing by 1000)

so.... 3mL = 3E-3L
34. how do you get # of moles from XmL of YM?
(x milliliters of y molar)
• XYE-3
• namely multyply X *Y *E-3so...
• Xml of YM = XYE-3 mol
35. to convert minutes to seconds.....
• multiply by 60.
• ..... or multiply by 6 and add a 0 at the end
36. shortcut to multiply any number by any multiple of ten.... 10, 20, 30, 40... 100, 200 300, 7000,
• multyply by the multiple of ten, and add same number of zeroes at end.
• 23*60 = 23*6(and an extra zero at the end) = 1380
• 23*60 =
37. shortcut to divide ugly numbers ... say 54/2228
• 1. reduce fraction as much as you can by breaking it in half as much as possible
• 2. if it gets ugly, like...54/228 = 27/1114, make the 27 a 26 and keep breaking it in halfs as much as possible
• 2. carry out regular division on smallest possible fraction.
• 54/2228 = 0.024
• Using my approach:
• 54/2228 ~ 54/2200 = 27/1100 ~ 26/1100 ~ 13/550 ~ 14/550 = 7/275 = 0.025
• This will certainly yield the answer
• ex2.
• division, 4/61 = 0.066
• if you do 4/61~4/60=2/30=1/15, and then do regular division you'll get 1/15 = 0.066
38. shortcut to divide a decimal by a big number.
Example... 0.55/204.2
• Express both with E's, and make the denominator smaller than the nominator by manipulating the E's, so..:
• 0.55/204.2 ~ 55E-2/2E2 ~ (55/2)E-4 ~ 27.5E-4

• Example from:
• how many moles are there in a 0.55gm sample of a compound whose molecular weight is 204.2 gm/mol -> there goes the quick

## Card Set Information

 Author: oardila ID: 94791 Filename: MCAT Mathematical tricks Updated: 2011-08-09 23:35:29 Tags: MCAT math Folders: Description: Mathematical tricks to overcome those tedious operations which sometimes slow us down solving physics and chem problems Show Answers:

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