is there a shortcut for half-life problems?

[orangeblossom]

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I understand the concept, but sometimes I can get bogged down if the given #s are given in scientific notation (like #30 on AAMC 10)

is there some way to set up a ratio or fraction or anything, other than just dividing a large number by 2 until I find the target # in order to figure out how many half-lives have elapsed?

or does everybody just divide by 2 until they figure it out?

 

[shaboobly]

I understand the concept, but sometimes I can get bogged down if the given #s are given in scientific notation (like #30 on AAMC 10)

is there some way to set up a ratio or fraction or anything, other than just dividing a large number by 2 until I find the target # in order to figure out how many half-lives have elapsed?

or does everybody just divide by 2 until they figure it out?

my one piece of advice: get used to scientific notation. it helps tremendously in the PS section. i can teach it to you very easily

the first number needs to be 1-9. when you figure out the powers, a positive exponent means you move the decimal to the right how ever many spaces the power is, when it is negative you move it to the left however many the power is. all these are powers of 10.

when you multiply or divide, you can take each number separate and do the first numbers, then the powers, or the powers then the numbers (the numbers are the one you use from 1-9)

another thing that will help is know the prefixes for all the different powers. this will tell you what each of the powers of 10 will be.

 

[orangeblossom]

thanks for the advice,

 

[MedPR]

I understand the concept, but sometimes I can get bogged down if the given #s are given in scientific notation (like #30 on AAMC 10)

is there some way to set up a ratio or fraction or anything, other than just dividing a large number by 2 until I find the target # in order to figure out how many half-lives have elapsed?

or does everybody just divide by 2 until they figure it out?

thanks for the advice, but do you have an answer to my question?

Use percentages. That's the shortcut.

 

[Big N Tasty]

EK literally suggests just counting them on your fingers. I wrote it off at first but tried it out in practice and it actually worked well. Saved a good amount of time too.

 

[Jepstein30]

EK literally suggests just counting them on your fingers. I wrote it off at first but tried it out in practice and it actually worked well. Saved a good amount of time too.

counting on your fingers works?

who knew...

 

[Big N Tasty]

counting on your fingers works?

who knew...

Yeah, but it's trickier sometimes since you can't use your thumbs.

 

[Jepstein30]

Yeah, but it's trickier sometimes since you can't use your thumbs.

why not 😕

 

[MedPR]

counting on your fingers works?

who knew...

why not 😕

Because a thumb is not a finger. It is a digit.

 

[Big N Tasty]

Because a thumb is not a finger. It is a digit.

This guy gets it lol

 

[karafox]

I didn't take AAMC10 yet, so I'm not sure if this is helpful...

I just divide by 2 and estimate the numbers via sketching a table. If the number falls into a certain range, the answers are typically far apart to justify it as the correct answer.