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? Let's answer step by step:
Each day it needs to consume 7 / 7 = 1 gallon of blood. There are 128 / 16 = 8 pints per gallon. So he needs to suck blood from 8 / 2 = 4 people per day. The answer: 4.