The two spirals

Logic Level 1

One of these spirals is formed with a single piece of rope that has its ends joined. The other spiral is formed with two separate pieces of rope, each with joined ends.

Can you tell which is made of single rope by using only your eyes? No fair tracing the lines with a pencil.

Courtesy: Think Fun

Left one Right one

Rohit Udaiwal by Rohit Udaiwal , 20, India

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Rohit Udaiwal
Jan 25, 2016

The spiral on the left is the single rope.

3 Helpful 0 Interesting 0 Brilliant 0 Confused
Ivan Koswara
Jan 25, 2016

Since the figure is symmetric, the one made with a single rope will have the center of the spiral to be inside of the figure (the only way the two ends of the spiral can meet). Now we can use ray casting algorithm , drawing a ray from the center of each spiral outward, to see that the first one crosses 5 or 7 lines while the second one crosses 4 or 6 lines. Thus the first one has the center of the spiral inside the figure, and hence is made up of one rope.

2 Helpful 0 Interesting 0 Brilliant 0 Confused

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...