Question 103d5

Oct 19, 2016

I got $50$

Explanation:

Consider the total as $x$ (corresponding to 100%); we can write that:
$\frac{x}{9}$ must be the same as (100%)/(18%)
or:
x/9=(100%)/(18%)
rearranging:
x=9*(100cancel(%))/(18cancel(%))=50

Oct 19, 2016

$50$

Explanation:

"Percent" literally means "per $100$". If we say something is 18%, that is the same as writing $\frac{18}{100}$. When we say 18% of a number, it is similar to how we might say $3$ of a number. In the latter case, we would multiply by $3$ to represent it algebraically. In this case, we multiply by 18% = 18/100.

Let $x$ represent our number. Writing our given information algebraically, then, we get

$\frac{18}{100} x = 9$

$\implies \frac{18}{100} x \cdot \frac{100}{18} = 9 \cdot \frac{100}{18}$

(we multiply by the reciprocal of the coefficient of $x$ to make $1$ the new coefficient of $x$)

$\therefore x = 50$

Oct 19, 2016

18% xx 50 = 9

Explanation:

You can work this out by writing an equation using $x$ as the unknown number.

18% " of what number is equal to " 9#?

$\frac{18}{100} \times x = 9 \text{ } \leftarrow$ now solve the equation for $x$

$x = 9 \times \frac{100}{18}$

$x = \cancel{9} \times \frac{100}{\cancel{18}} ^ 2$

$x = 50$