More tracings

Level 1

How many ways are there to trace this figure without lifting your pencil or adding anything?

54 27 1 infinitely many 32 2 0

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2 solutions

V I S I O N .
Jan 31, 2019

You have to start from the straight line from either vertex as they both have odd connections(YOU C.ANT START ON THE CIRCLE , you cant trace it then)if we start from the left one we will still end up on the right one so , the ways from right vertex = ways from left vertex.

So now we are on right vertex & we have 2 choices , either to go up or go down on the circle , lets say we go up & then on next intersection we have same situation. So we have two choices on each intersection & we have 4 of these so total ways = 2x2x2x2 = 16 ( When coming back we take the path we left so there is no choice when coming back) . So 16 from right vertex & 16 from left one so the answer is 32.

I might have missed something completely, but how come we can't start at any point? The question didn't specify that, nor that we can't overlap.

RedRoachDK Celinder - 2 years, 4 months ago
K T
Feb 1, 2019

There are two points which have an odd number of lines connecting to them: either end of the straight line. These will have to be the starting and end points. Where to start then is a binary choice. The first three circles have to be made half, and can only be completed after the last one. But for each circle we have a binary choice: clockwise or counterclockwise. All 5 choices can be made indepently. 2 5 = 32 2^5=\boxed{32}

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