Crosses

Question:

Two creepers, one jasmine and the other rose, are both climbing up and round a cylindrical tree trunk. The jasmine twists clockwise and the rose anti-clockwise, and they both start at the same point on the ground. Before they reach the first branch on the tree the jasmine has made 5 complete twists and the rose 3 twists. Not counting the bottom and the top, how many times do they cross?

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.

C

A

P

T

A

I

N

I

N

T

E

R

V

I

E

W

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Answer: Seven: The best way to find the solution to this problem is to make a practical experiment.
Make a vertical cut in the tree trunk and peel off the trunk to form a long rectangle. Across the rectangle draw 5 parallel lines to represent the jasmine and another parallel line for the rose. Then you will be able to see the seven crossing positions.

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