each set has 4 even numbered cards
coral reefs are the most diverse of all marine ecosystems. teem with life, with perhaps one-quarter of all ocean species depending on reefs for food and shelter. is a remarkable statistic when you consider that reefs cover just a tiny fraction (less than one percent) of the earth’s surface and less than two percent of the ocean bottom. because are so diverse, coral reefs are often called the rainforests of the sea.
coral reefs are also very important to people. the value of coral reefs has been estimated at 30 billion u.s. dollars and perhaps as much as 172 billion u.s. dollars each year, providing food, protection of shorelines, jobs based on tourism, and even medicines.
unfortunately, people also pose the greatest threat to coral reefs. and destructive , pollution, warming, changing ocean chemistry, and invasive species are all taking a huge toll. in some places, reefs have been entirely destroyed, and in many places reefs today are a pale shadow of what once were.
let us denote the number of pet fish in the united states by f. it is given that 1
let us denote the number of pet reptiles in the united states by p. it is given that 2
now, to find how many pet fish and reptile pets are in the united states all together in the scientific notation, we will have to add equation 1 and equation 2. even before we do that we can see that the "order of magnitude" of f is significantly than that of p. thus, we can straightforward say that the answer will approximately be:
let us show in a detailed :
thus, the answer in scientific notation is: