Five hundred cockroaches of one species were sprayed with a new insecticide. Twenty-four hours later nearly all the cockroaches were dead. A few, however, survived. This outcome illustrates which one of darwin’s key ideas about natural selection and variation?.

Amedium water hose can fill a pool in 30 minutes. a larger water hose can fill the same pool in 20 minutes. if both hoses are turned on at the same time, how long will it take to fill the pool? -what equation can be used to solve this work problem? -how many minutes will it take both hoses to fill the pool?