Dividing Decimals

[FrkyBgStok]

I have no troubles multiplying decimals but I need a hand figuring out a quick and easy way to divide decimals. Like concentrations. For example, .0015/.25. is there a quick way that you guys can look and say, "hey, that's .006?" This is killing my score.

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[afruff23]

I have no troubles multiplying decimals but I need a hand figuring out a quick and easy way to divide decimals. Like concentrations. For example, .0015/.25. is there a quick way that you guys can look and say, "hey, that's .006?" This is killing my score.

Well, a good way is to know your fraction->decimal and decimal->fraction conversions well.

For your problem, I would instantly recognize 0.25 as 1/4. From there, dividing 0.0015 by 1/4 is the same as multiplying 0.0015 by 4 which equals 0.0060 (yes I know mcat has no sig figs, but I but them anyways).

 

[Entadus]

Try scientific notation. For example:

0.04/0.000032

Becomes

(4 x 10^-2) / (3.2 x 10^-5)

which may be easier since:

(4 / 3.2) x 10^(-2+5)
is easily recognizable as approximately:

~1.3 x 10^3

 

[LebLlama]

Well, a good way is to know your fraction->decimal and decimal->fraction conversions well.

For your problem, I would instantly recognize 0.25 as 1/4. From there, dividing 0.0015 by 1/4 is the same as multiplying 0.0015 by 4 which equals 0.0060 (yes I know mcat has no sig figs, but I but them anyways).

beautiful. this is the type of thinking that i need to work on. these questions hurt my score too.

 

[addo]

scientific notation makes everything so much easier.
to do your example-
.0015/.25=15*10^-4/25*10^-2
which becomes (15/25)*10^-4*10^2=3/5*10^-2=.006
Just remember to switch the sign on the exponent when you move it up. Also, know all fractions up to like 1/20=.05