Can you figure out easy-looking math sum in 30 seconds by remembering the special rule?

The answer to this mathematical brain teaser is NOT 40 - can YOU solve it in 30 seconds by remembering the special rule?
Edutopia

4 Ways to Bring Logic Puzzles Into Your Math Class

Take the pressure off of problem-solving with engaging thinking games that encourage students to work together to find ...
IEEE

Design of a Quantum Walk Circuit to Solve the Subset-sum Problem

Abstract: Search algorithms based on quantum walks have emerged as a promising approach to solve computational problems across various domains, including combinatorial optimization, and cryptography.
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Using crystal clear ice to freeze my finger

How to make your finger look completely frozen! Unusual reasons people have filed for divorce Easy-looking math sum leaves people confused - can you solve it without a calculator? Abu Dhabi Police ...
IEEE

An Iterative Threshold Algorithm of Log-Sum Regularization for Sparse Problem

Abstract: The log-sum function as a penalty has always been drawing widespread attention in the field of sparse problems. However, it brings a non-convex, non-smooth and non-Lipschitz optimization ...