Really Big Lights – A math problem

Here’s a really big problem you can work on with your students this holiday season.

Act 1:
Show them this video and ask: What do you notice? What do you wonder?

After allowing them to voice their noticing and wonderings guide them to wonder: How big is that new light? How many times bigger is the big light compared to the old light? How many Really Big Lights would you have to put up to cover the same length as last year?

Act 2: Here are some images to help make some conclusions:

Guess: How long is the big light? How many times longer is the big light than the small light?




Guess: How many small lights are in one string that stretches 15 feet?




Work together to determine how many Really Big Lights would replace the string of 50 lights? What assumptions will you make?

Act 3: Reveal


Why might your calculated answer be different from the answer shown?

If you had 50 Really Big lights how long would could they reach? How many cars could you put in that garage?

Grab all files for this activity

You can see more info about the lights over at

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5 thoughts on “Really Big Lights – A math problem

  1. Thank you very much for posting this! 🙂 Have you done it with your students? How did it go?

    It just so happens that the topics of your recent posts address exactly what I’m focusing my attention on for teacher training purposes. I plan on using your Really Big Lights Task as an introduction to 3 Act Tasks on Friday. Your willingness to share is very appreciated!

    (I was also wondering about the 1 ft measurement. On the site, the measurement is 14.5 inches.)

    1. Jon Orr

      I believe the hook at the top account for the extra 2.5 inches. Since the small bulb doesn’t have that I didn’t measure it.

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