Zeno's Other Frog

Calculus Level 3

Zeno's frog jumps twice as far each jump. During the first hop, Zeno's frog can hop exactly one foot.

How many hops will Zeno's frog have to take to move googol feet?

Assumptions: A googol is a 1 with 100 zeroes after it. During the first hop the frog moves forward one foot. During the second hop, the frog will move forward two feet. After the second hop, the frog's total displacement is three. Therefore, it takes two hops to move three feet.


The answer is 333.

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4 solutions

Kumar Saurav
Dec 26, 2014

1+2+ . . . +2^(n-1)>=10^100 =>2^n-1=10^100 100/log(2) (base 10) is little over 332 but less than 333 so answer is 333

Shawn Davies
May 12, 2015

I did this with help from excel, made 3 columns. 1 to track the # of jumps, 1 to track the distance of the current jump and 1 to track the total distance. I noticed a pattern pretty quickly as well.

Jump 2 was a distance of 2ft and a total distance of 3ft. Jump 3 was a distance of 4ft and a total distance of 7ft. Jump 4 was a distance of 8ft and a total distance of 15ft. Jump 5 was a distance of 16ft and a total distance of 31ft. Jump 6 was a distance of 32ft and a total distance of 63ft.

The total distance is always 1ft less than the length of the current jump x2. After noticing that I was able to drag the formula down until the jump distance was over half a googol, which happens at jump 333.

Brock Brown
Dec 25, 2014

Approached with 10 lines of Python:

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googol = 10**100
traveled = 0
jump_distance = 1

for i in xrange(1,1500):
    traveled += jump_distance
    jump_distance *= 2
    if traveled >= googol:
        print "The frog is beyond googol."
        print 'hop:',i
        break

Christopher Hsu
May 12, 2015

2^jumps = 10^100

333 to exceed a googel

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