Building marble runs is a blast. It feels great to set up ramps, drop a marble at the top and watch it bounce and roll all the way to the end. Now imagine building a marble run that moves thousands of marbles at a time! Jelle Nikkers, who lives in the Netherlands, put together giant slides, zigzag ramps and tipping seesaws to make a giant machine that moves 11,000 marbles at a time. The marbles roll onto a moving ladder that carries 17 on each rung, then dumps them out at the top onto the ramp. Check out the video to see the marbles do all kinds of tricks, and to hear the rushing river-like sound they make!

*Wee ones:* Which has *fewer* marbles, a seesaw holding 5 marbles or a seesaw holding 7 marbles?

*Little kids:* The first seesaw shown tips when it fills with 10 marbles. If 6 have rolled onto it so far, how many more are needed to tip it? *Bonus:* The machine holds 13,000 marbles total, with 11,000 on the move at once. How many marbles are sitting around waiting their turn?

*Big kids:* The whole marble run is 33 feet long and 4 feet wide! If you and your friends are all 5 feet tall, how many of you have to lie head to toe to stretch longer than the marble run? *Bonus:* If it fits inside a perfect rectangle, how far is it to walk all the way around it?

Answers:

*Wee ones:* The one holding 5 marbles.

*Little kids:* 4 more marbles. *Bonus:* 2,000 marbles.

*Big kids:* 7 of you, since 6 of you will stretch only 30 feet. *Bonus:* 74 feet, since you have to walk the 33 twice and the 4 twice.