# What number is 70% of 45?

Sep 30, 2016

$31.5$

#### Explanation:

By definition, 70% means "seventy parts over a hundred$o f s o m e t h \in g , \mathmr{and} a g a \in , t h i s m e a n s t \hat{y} o u \mu s t \div i \mathrm{de} y o u r q u a n t i t y \in$100$\pi e c e s , \mathmr{and} t h e n c o n s i \mathrm{de} r o n l y$70 of those pieces.

This should clarify how we must behave:

• Divide $45$ in a hundred parts: $\frac{45}{100} = 0.45$. This is a part every $100$ of $45$, namely the 1% of $45$.

• We want $70$ of these little pieces, so we take $0.45 \cdot 70 = 31.5$. This is the 70%# of $45$.