400 is 10% of 4000.
Step 1: Translate the words into an equation.
400 | is | what percent | of | 4000 |
400 | = | x | $ \cdot $ | 4000 |
Step 2: Solve for $ x $.
$$ \begin{aligned} 400 &= x \cdot 4000 \\[1.2 em] 4000 \cdot x &= 400 \\[1.2 em] x &= \dfrac{ 400 }{ 4000 } \\[1.2 em] x &= 0.1 \end{aligned} $$Step 3: Express $ x $ as a percentage.
$$ x = 0.1 = 0.1 ~~\cdot~~ 100 \% = 10 \% $$