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Difficulty: Taxing

Here’s a beautiful artwork from 1895, titled Mental calculation. In public school of S. A. Rachinsky, painted by Nikolay Bogdanov-Belsky.

Can you solve the puzzle the kids are pondering?

If you can’t quite see the equation, here it is:

Scroll down or click for a hint, or the answer!

Brainteaser hint

• Although the kids in the painting are trying to do it in their heads, you can always use a pencil!
• Remember that teachers often like questions with nice round answers.
• 10² means 10 x 10. Calculate these first!

Brainteaser answer

The answer is 2.

Here’s the working:

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