Twitter-Length Tasks – In-App Purchases

Twitter-Length Tasks can be quickly and simply explained, yet allow for extensive exploration.

calcI recently downloaded a calculator app on my phone. Then I was surprised that I could only use a few keys – the rest of the keys were only available as in-app purchases.

  • The black keys were included for free.
  • The red keys cost $1 each.
  • The blue keys cost $3 each.
  • The green keys cost $5 each.

What is the cheapest way to display a 10 on the calculator?

What about 0.25?

How many different numbers can you display for free?

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