46 = n + n + 2 + n + 4 + n + 6
46 = 4n + 12
34 = 4n
n = 8.5
Is it definitely 46?
Here, Twice fast means, she takes half time in doing same amount of work.
Let, Anna takes = 2t & Jane takes = t
It would be: 1/t + 1/2t = 1/15
2t + t / 2t² = 1/15
15(3t) = 2t²
2t² = 45t
Divide both sides by t,
2t = 45
t = 45/2
t = 22.5
& 2t = 22.5(2) = 45
In short, Anna would take 45 minutes
Hope this helps!
There are two of them.
I don't know a mechanical way to 'solve' for them.
One can be found by trial and error:
x=0 . . . . . 2^0 = 1 . . . . . 4(0) = 0 . . . . . no, that doesn't work
x=1 . . . . . 2^1 = 2 . . . . . 4(1) = 4 . . . . . no, that doesn't work
x=2 . . . . . 2^2 = 4 . . . . . 4(2) = 8 . . . . . no, that doesn't work
x=3 . . . . . 2^3 = 8 . . . . . 4(3) = 12 . . . . no, that doesn't work
<em>x=4</em> . . . . . 2^4 = <em><u>16</u></em> . . . . 4(4) = <em><u>16</u></em> . . . . Yes ! That works ! yay !
For the other one, I constructed tables of values for 2^x and (4x)
in a spread sheet, then graphed them, and looked for the point
where the graphs of the two expressions cross.
The point is near, but not exactly, <em>x = 0.30990693...
</em>If there's a way to find an analytical expression for the value, it must involve
some esoteric kind of math operations that I didn't learn in high school or
engineering school, and which has thus far eluded me during my lengthy
residency in the college of hard knocks.<em> </em> If anybody out there has it, I'm
waiting with all ears.<em>
</em>
