It is a very convenient way to write down very large or very small numbers like 10³ = 1000, so 4 × 10³ = 4000. So you can write 4000 = 4 × 10³ in standard form. Standard form =6.543 x 1000 = 6.543 x 10 ³  Expanded form = 6 x 1000 + 5 x 100 + 4 x 10 + 3.