Let us define a fraction tower be fraction like this: 1 2 4 8
That is, when we look from top to bottom, the fraction line is shorter and shorter and the numbers are decreasing power of 2.
What is the value of fraction tower with
2
2
0
1
6
at the top?
Let the answer be
2
A
, enter
A
as your answer.
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Cool pairing-up solution!
Actually when I solve it myself, I look for a pattern:
1
-level
=
1
2
-level
=
2
3
-level
=
2
4
-level
=
4
...
2
0
1
7
-level
=
2
⌊
2
2
0
1
7
⌋
=
2
1
0
0
8
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I got that too. But then I noticed it is easier to understanding by flipping the fractions.
The first step is already invalid. 8/4/2/1 is equal to, according to the way you did, (8/4) * (1/2) not (8/4)*(2/1)
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Could you explain a bit more why it should be 4 8 × 2 1 ?
It's definitely 4 8 × 1 2 .
An easy way to see it is
1 2 4 8 = 8 ÷ 1 2 4 = 8 × 4 1 2 = 4 8 × 1 2 .
Okay guys, the way I solved it was probably not the most efficient way, but it is pretty intuitive.
What I like the most is that it is easy to see the pattern here.
So the general answer of this tower fraction for 2 n , were n ∈ N is 2 ⌈ 2 n ⌉ .
Obs: Sorry for my handwriting, when I wrote this I was trying to make sense to myself, just later that I thought of posting this solution (regardless the fact that there were already other excellent solutions).
Obs2:
⌈
n
⌉
denotes the ceiling function.
Congrats on guessing the general formula. How can we prove it?
Nice graph! Plotting a graph can help us find a pattern.
Congrats on guessing the general formula. How can we prove it?
Let f ( x ) the function defined as the fraction tower with x at the top. f ( a b ) = a 2 b if b is an even number, so f ( 2 2 0 1 6 ) = 2 1 0 0 8
Can you prove this?
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If you start to divide from the first terms you will find that a a 2 = a So the next division will be a a 3 = a 2 a 2 a 4 = a 2 a 2 a 5 = a 3 a 3 a 6 = a 3 Etc, more than a proof for that "property" is a pattern
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We note that the 4 -level fraction tower can be written as 1 2 4 8 = 4 8 ⋅ 1 2 .
Therefore, the 2 0 1 7 -level fraction tower is as follows:
Q = 2 2 0 1 5 2 2 0 1 6 ⋅ 2 2 0 1 3 2 2 0 1 4 ⋅ 2 2 0 1 1 2 2 0 1 2 ⋅ . . . 2 5 2 6 ⋅ 2 3 2 4 ⋅ 2 1 2 2 = n = 1 ∏ 1 0 0 8 2 2 n − 1 2 2 n = n = 1 ∏ 1 0 0 8 2 = 2 1 0 0 8
⇒ A = 1 0 0 8