Have you ever slid down a water slide? Well, here’s your chance to ride UP the slide. The “Flow Rider” pumps water up a slippery hill at high speed, while swimmers fling themselves onto it on surfboards. Some people swim on their bellies, but the brave ones stand on their boards to surf. How much water does it take to make a wave like this — and how long can you ride it without wiping out?

*Wee ones:* On which side of that photo is someone already sliding, the left or the right?

*Little kids:* Only 1 kid at a time can ride on one side. If 4 extra people join in, how many riders would that side have? *Bonus:* If 2 of those were surfing instead of bellyboarding, how many would be bellyboarding?

*Big kids:* If 8 people are in line in front of you and a new person starts every 5 minutes, how long do you have to wait for your turn? *Bonus:* If you try to stand on your surfboard every 3rd ride starting with the 3rd, will you surf on your 42nd turn?

*The sky’s the limit:* We’re told that it costs about $500,000 to build a Flow Rider. How does that relate to a million dollars? And how many of these could a hotel chain build for $10 million?

Answers:*Wee ones:* On the right.

*Little kids:* 5 riders. *Bonus:* 3 bellyboarders.

*Big kids:* 40 minutes.* Bonus:* Yes! 42 is a multiple of 3. You can tell because its digits add up to a multiple of 3 themselves: 4 + 2 = 6.

*The sky’s the limit:* $500,000 is half a million, so for $1 million they can build 2 Flow Riders. That means $10 million can build 20 of them.