Squaring Ends in 5
Instantly square numbers ending in 5
65 × 65 = 4225
65 × 65 is a square split at the tens: 3600, 300, 300 and 25.
The 3600 and both 300s make 60 × 70 = 4200. Only the 25 is left.
So the recipe: tens digit × one more, then attach 25. .
Your turn
Three to try in your head — tap what you get.
165 × 165
55 × 55
85 × 85
All 36 shortcuts: the Magic Tricks library.