The fast method
⚡
24 × 10 = 240; halve to get 120.
How it works
Multiply by 10, then halve the result. 5 = 10 / 2, so 5n = 10n / 2.
Why it works
5 = 10 / 2, so 5n = 10n / 2.
Use it when
Works for any real number.
Watch out for
Keep the half when the number is odd.
Verified examples
Example 1
24 × 5
24 × 10 = 240; halve to get 120.
120Example 2
37 × 5
37 × 10 = 370; halve to get 185.
185Example 3
86 × 5
86 × 10 = 860; halve to get 430.
430