mcat math: how fast can you do this problem?

[theCLE]

This math problem took me over 2 minutes to conquer 🙁

Now it's your turn


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1.68/84


what is your methodology?

thanks!

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[jakobinarino]

0.02 = 1.68 x 100 = 168 / 84 = 2 / 100

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[Trayshawn]

^pretty clever. But thats only if you noticed that 1.68 is a multiple of 84 when you multiply it by 100.
If you didn't, you could just rely on the fact that rough approximations are okay on the MCAT.

I'd round 1.68 up to 2. Then you'd get 2/84 = 1/42. Keep in mind that this value is slightly larger than actual (since you rounded up). Then I'd round 42 down to 40 to kind of make up for the previous rounding up (there's no way to tell which rounding affected your answer the greatest, but it doesn't matter. you just want a ballpark answer).

So you now have 1/40 which is the same as (1/4)/10 or .25/10 --> .025. The other answer choices will probably be like .09 or something. So .025 is close enough.

This might seem complicated but, in situations where you can't do the neat little trick the guy above me just did, this could be a HUGE time saver over doing the full out long division.

 

[PhysMatMan]

Or you could figure out what some multiples of 84 are and round up to those.

Eg 1.68/85 ~1.70/85

 

[BABSstudent]

This math problem took me over 2 minutes to conquer 🙁

Now it's your turn


ready?

go...



1.68/84


what is your methodology?

thanks!

1.68/84

I noticed immediately that 168 is double 84, so the answer has a 2.

Now to get 168 from 1.68, I multiplied by 100. That means I have to divide the final 2 by 100.

2/100 = 0.02

Answer took about five seconds.

 

[gettheleadout]

1.68/84

I noticed immediately that 168 is double 84, so the answer has a 2.

Now to get 168 from 1.68, I multiplied by 100. That means I have to divide the final 2 by 100.

2/100 = 0.02

Answer took about five seconds.

I also took about 5 seconds, but I didn't even notice the ratio.

I just looked and saw a very small number and a (relatively) very big number. I went to the closest factor that came to mind, being 1/100 of the big number or .84, and then realized that the numerator was double this factor. 2 X 1/100 = 2%

 

[HardWork1]

This math problem took me over 2 minutes to conquer 🙁

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1.68/84


what is your methodology?

thanks!

You could use scientific notation

1.68/84

(168.0 x 10^-2)/(84 x 10^0)= 2 x 10^-2=0.02.

or

(16.8 x 10^-1)/(8.4 x 10^1)= 2 x10^-2= 0.02

 

[Redpancreas]

This math problem took me over 2 minutes to conquer 🙁

Now it's your turn


ready?

go...



1.68/84


what is your methodology?

thanks!

a.) 1.68/2=.84

b.) .84/84= 1/100 = 1%

c.) multiply the 2 back to get 2%

 

[MedWonk]

0.02 = 1.68 x 100 = 168 / 84 = 2 / 100

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This is similar to how I thought of it. Took about 10 seconds.

I can do this because of practice, though. I'm not a math whiz. After going through practice passages and doing math in my head, things start to click 3 months in.

 

[Qester]

Took me about 5 seconds..

84 goes into 168 twice... Then I need to add two decimal places since I removed them making 2=.02

 

[BerkReviewTeach]

This is such a great math question. It's perfect for what test writers are aiming to do. Some people see the ratio right away (5 seconds to see the solution) while others don't see it. This separates people on the curve, which makes for a great style of question.

 

[theCLE]

This is such a great math question. It's perfect for what test writers are aiming to do. Some people see the ratio right away (5 seconds to see the solution) while others don't see it. This separates people on the curve, which makes for a great style of question.

Got it from TBR chem! Thank you for all the great responses!