The fast method
⚡
72 ÷ 4 × 100 = 1,800
How it works
Since 25 is one quarter of 100, replacing ×25 with ÷4 ×100 keeps the value unchanged.
Why it works
25 = 100 ÷ 4, so n × 25 = n ÷ 4 × 100.
Use it when
Fastest when the number is divisible by 4.
Watch out for
If it is not divisible by 4, fractions may be less convenient.
Verified examples
Example 1
Calculate 72 × 25
72 ÷ 4 = 18; 18 × 100
1800Example 2
Calculate 48 × 25
48 ÷ 4 = 12; 12 × 100
1200Example 3
Calculate 36 × 25
36 ÷ 4 = 9; 9 × 100
900