477: How Many Knots?

from NCTM:

How many knots will form if you pull the ends of the string in opposite directions?

199: What is that shape?

Is this one shape or three?

141: Topology Bagels - One Ring

Yesterday's cutting was interesting, but difficult to achieve. This one is simpler. Can you cut your bagel so that you get one continuous loop of bread?

For Sunday brunch, cut your bagel so the two halves are linked together like a chain.
— Steven Strogatz (@stevenstrogatz)

140: Topology Bagels - Two Rings

Can you cut your bagel so that you get two linked rings?

For Sunday brunch, cut your bagel so the two halves are linked together like a chain.
— Steven Strogatz (@stevenstrogatz) May 25, 2014