Grades 3–8
Mental Math & Puzzles
Mental-math shortcuts and classic puzzles, each with a picture that shows why it works and a test-ready write-up.
Multiply 23 × 27 in 3 Seconds
Multiply 37 × 77 in 3 Seconds
×11 in 3 Seconds: Pull Apart, Add the Middle
35 Heads, 94 Legs: A 1,500-Year-Old Puzzle, 3 Ways
49 × 51 in Your Head? Cut One Strip and It's Easy
Square Any Number Ending in 5 in Your Head (35², 75²…)
Add 1 to 100 in Seconds: Gauss's Trick (With a Picture)
Can You Pass Chinese 6th Grade Math? (3 Real Exam Questions)
Sum of Odd Numbers From 1 to 99 in 5 Seconds (Formula: n²)
