Question 309600
A machine can fill 3864 cartons of milk in 0.4 hour. How many cartons of milk can it fill per hour?
<pre><font size = 4 color = "indigo"><b>

"In" here means "per", so
</pre></font></b>
3864 cartons of milk in 0.4 hour 
<pre><font size = 4 color = "indigo"><b>
means

3864 cartons of milk PER 0.4 hour

"PER" means "divided by" or "over":

{{{(3864cartons)/(0.4hour)=(3864/0.4)(cartons/hour)=9960(cartons/hour)}}}

or 9960 cartons per hour.

Edwin</pre>