Question

do now: in a group, 65% is 16 yo 35% is 18 yo. what is the average age?

Explanation:

Step1: Convert percentages to decimals

$65\% = 0.65$, $35\%=0.35$

Step2: Use weighted - average formula

The weighted - average formula is $\text{Average}=w_1x_1 + w_2x_2$, where $w_1$ and $w_2$ are the weights (proportions) and $x_1$ and $x_2$ are the values. Here, $w_1 = 0.65$, $x_1=16$, $w_2 = 0.35$, $x_2 = 18$.
$\text{Average}=0.65\times16+0.35\times18$
$=10.4 + 6.3$
$=16.7$

Answer:

$16.7$