D
deleted74029
I know the math on the MCAT is fairly simple, I was confronted with finding the cube root of 5 x 10-7 anyone know how to find cube roots fairly quickly? This kinda slowed me down.
- Joined
- Jul 2, 2008
- Messages
- 12
- Reaction score
- 0
All you have to do is cube the mantissa and multiply the exponent by 3.
(6.0 X 10^4)^2= (6)^2 x 10^4 x 2= 36.0 X 10^8= 3.6 X 10 ^9
There really isnt a quick way this way should be fairly quick though. Hope this helps!!😀
(6.0 X 10^4)^2= (6)^2 x 10^4 x 2= 36.0 X 10^8= 3.6 X 10 ^9
There really isnt a quick way this way should be fairly quick though. Hope this helps!!😀
- Joined
- Oct 17, 2007
- Messages
- 5,474
- Reaction score
- 56
There is probably an easier way to estimate this than what I'll post below, but here it is anyway.
So you need to cube root the mantissa, and divide the exponent by 3 to take a cube root.
The first thing I do is "fudge" the exponent to a number that is easily divisible by 3. In this case "-9" is easily divisible by three. So the number becomes:
5 x 10^-7 = 500 x 10^-9
Then I estimate the cube root of the mantissa:
So 7 cubed is 343, and 8 cubed is 512. Since 500 is really close to 512, cube root 500 is probably about 7.9.
Now divide the exponent by three and use your estimated mantissa:
Cuberoot(5 x 10^-7) = Cuberoot(500 x 10^-9) ~= 7.9 x 10^-3
Actual answer: 7.937 x 10^-3
