I can't do MCAT math!

[Jezzielin]

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Ok, in the PS par tof the test I have the worst time doing "easy math".

EX:
3x10^8/550x10^-9 = 5.4x10^14

How can you figure this out in your head??? I thought in dividing you divide the base number and subtract the exponent. Am I wrong? 😕

 

[Tinker Creek]

Ok, in the PS par tof the test I have the worst time doing "easy math".

EX:
3x10^8/550x10^-9 = 5.4x10^14

How can you figure this out in your head??? I thought in dividing you divide the base number and subtract the exponent. Am I wrong? 😕

Yea, but to make things simple, where the choices aren't close enough I would just round the denominator to 6 X 10^-7 and divide 3 by 6 and subtract the exponents (8 -( -7), and move one decimal place to right.

 

[Axe]

Learn to use scientifc notation. Basically youre just adding and subtracting exponants and multiplying and dividing between single digits.

 

[Medikit]

This is how I would do it.

550 is about half of 1000.

So work out 3x10^8/1000x10^-9 aka 3x10^8/10x10^-6= 3x10^14. Now multiply by 2 to correct the change we made and we get 6x10^14. Since 550 is bigger than 500 we are actually a little less than 6x10^4, so look for an answer between 5 and 6x10^14. You should be able to do that math pretty quickly.

 

[Kazema]

Yea, but to make things simple, where the choices aren't close enough I would just round the denominator to 6 X 10^-7 and divide 3 by 6 and subtract the exponents (8 -( -7), and move one decimal place to right.

Yeah, the key is to realize that 550x10^-9 is the same as 5.5x10^-7. 3/5.5 is much easier than 3/550.

Or you could do 0.55x10^-6. So then you're doing 3/.55 which is a little less than 3/.5.

Scientific notation is neat-o.

 

[skicu]

Always simplify the scientific notation and if you are still unsure, round to the easiest number to deal with. The MCAT answers are set up so that you can do this without a problem. This approach worked really well for me on the MCAT a couple of years ago.

 

[Docstrange]

yeah I had this problem and was basically stuck at a 10 because I would never get the math problems right. I would suggest practicing 10 or 15 problems with exponents a day so it becomes second nature.

 

[stoleyerscrubz]

Good advice. I got killed on a practice mcat because my answers were not matching to the choices.

yeah I had this problem and was basically stuck at a 10 because I would never get the math problems right. I would suggest practicing 10 or 15 problems with exponents a day so it becomes second nature.

 

[psiyung]

Ok, in the PS par tof the test I have the worst time doing "easy math".

EX:
3x10^8/550x10^-9 = 5.4x10^14

How can you figure this out in your head??? I thought in dividing you divide the base number and subtract the exponent. Am I wrong? 😕

just convert 3X10^8 to 3000 X 10^5

3000/550 or 30/5.5 which is close to 5.5

now take 10^5/10^-9 --> 10^14