## Multiplication of two numbers that differ by 2

### (This trick only works if you have memorised or can quickly calculate the squares of numbers. When two numbers differ by 2, their product is always the square of the number in between these numbers minus 1.Let me explain this rule by taking examples

18*20 = 19^2 - 1 = 361 - 1 = 360

25*27 = 26^2 - 1 = 676 - 1 = 675-
## Example.

Understand the rule by 1 more example 49*51 = 50^2 - 1 = 2500 - 1 = 2499 -
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