A vampire needs to suck 7 gallons of blood per week to survive.  If he sucks 2 pints of blood per person, how many people does he need to suck each day to survive?
Each day it needs to consume 7/7=
<gadget id="calculator">7/7</gadget>
<output>1</output>
1 gallon of blood.
There are 128/16=
<gadget id="calculator">128/16</gadget>
<output>8</output>
8 pints per gallon.
So he needs to suck blood from 8/2=
<gadget id="calculator">8/2</gadget>
<output>4</output>
4 people per day.

<result>4</result>