The formula is P=2(w+h){\displaystyle P=2(w+h)}, where P{\displaystyle P}  equals the perimeter of the rectangle, w{\displaystyle w} equals the width of the rectangle, and h{\displaystyle h} equals the height of the triangle. If you don’t know the length of the width and height of the rectangle, you cannot use this formula. You can also use the formula P=a+b+c+d{\displaystyle P=a+b+c+d}, where each variable is equal to the length of one side of the rectangle. Due to the commutative property, it doesn’t matter which measurement you use for the width, and which you use for the height. The width and height are two adjacent sides. If the rectangle is not a square, these to side lengths must be different. For example, if a rectangle has a width of 5 cm and a height of 10 cm, your formula will look like this: P=2(5+10){\displaystyle P=2(5+10)}. Make sure you follow the order of operations and complete the calculation in parentheses before multiplying. The resulting value will give you the perimeter of your rectangle. For example:P=2(5+10){\displaystyle P=2(5+10)}P=2(15){\displaystyle P=2(15)}P=30{\displaystyle P=30}So, the perimeter of the rectangle is 30 cm. In this formula x{\displaystyle x} is equal to the length of one side of the square. A square has 4 equal sides, so to find its perimeter, you only need to multiply the length of one side by 4. For example, if a square has one side that is 3 cm long, to find the perimeter, you would calculate P=4(3)=12{\displaystyle P=4(3)=12}. So, the perimeter is 12 cm. Often you will not be given the length of all sides, or even the length of any side. It still may be possible to  find the perimeter of a rectangle.  If you know the area of the rectangle, and the length of one side, you can find the perimeter by finding the missing width or height using the area formula. Set up the formula A=wh{\displaystyle A=wh}. Plug in the values you know, then solve for the missing variable. Now you know the length and width, so you can use the perimeter formula. If you know one side length and the length of the diagonal, you can use the Pythagorean Theorem to find the missing side length. Set up the formula a2+b2=c2{\displaystyle a^{2}+b^{2}=c^{2}}. Substitute the length of the diagonal for c{\displaystyle c}, and the side length for a{\displaystyle a}. Solve for b{\displaystyle b}. Now you know the length and width, so you can use the perimeter formula.
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One-sentence summary -- Set up the formula for the perimeter of a rectangle. Plug the width and height into the formula. Add the length and width, and multiply by 2. Use the formula P=4x{\displaystyle P=4x} to find the perimeter of a square. Find the perimeter given other information.

Article: Avoid single-serve or individually wrapped items. Shop at stores that have bulk dispensers for grains, nuts, dried fruits, and snacks. Bring your own plastic bag or container to put the bulk food in. And try to buy bulk sizes of food or sanitary products, which saves on packaging.  When buying produce at the grocery store, avoid packing the product in an extra plastic bag if it isn’t necessary. Vegetables such as potatoes, onions, peppers, tomatoes, beets; and fruits such as bananas, apples, plums, and melons shouldn’t require an extra bag. Instead of buying canned soup or pasta sauce, read up in a cookbook how to prepare them at home. Practice “precycling” by only buying products whose materials can be recycled. Take durable canvas or synthetic-fiber bags, a backpack, or a basket with you to the store, enough to hold whatever you plan on buying. These can usually be bought at the stores themselves. A heavy-duty plastic bag that you use multiple times can serve the purpose almost as well. Disposables contribute large amounts of waste to our environment. They include things like plastic forks, knives, plates, and cups. They also include things like diapers and razor blades. Instead of buying items that you'll throw away after using them, buy items that you can use again and again. For example:  Instead of using disposable diapers, try cloth diapers or nappies. You will have to clean them more often, but you'll reduce waste. Get a razor with replaceable blades rather than a disposable razor. You'll still have to throw the old blades away, but you'll save the plastic handle. For picnics, serve with re-usable plastic or wooden plates, cups, and utensils instead of disposable paper or plastic ones. Turn off or unplug any electrical appliances that aren't being used, such as the TV, radio, stereo, computer, lights, or chargers for cellphones or mp3 players. Try to wash clothes by hand, and dry them outside as much as possible. And if you purchase appliances, such as dishwashers, washing machines, and dryers, choose ones that are rated with the Energy Star classification.  Replace all incandescent lightbulbs with Energy-Star-rated compact fluorescent lightbulbs (CFLs), which can save you $6 in energy costs per year.  Try towel drying your hair instead of blow-drying it. If it is cold inside your residence, just put on a jacket or sweater instead of turning up the heat. Try to reduce your shower time to between 5 and 10 minutes. Turn off the water when shampooing or scrubbing. Take fewer baths as well, since they can consume more water than a short shower. When you brush your teeth, turn off the faucet between soaking and rinsing the brush. If you’re receiving junk mail, call the sending company’s 800 number, usually found on the offer or order page, and ask to be removed from their mailing list.  Request electronic bill instead of paper ones for all your utilities, member dues, and other periodical payments. You can choose this when signing up for an account. If you are already receiving paper bills, it is not too late to change. Access your account online or by phone, and see if you can switch to electronic bills instead. Try to walk, bike, or take public transit to school or work. If possible, invest in an electric or hybrid vehicle--these options are more fuel-efficient and emit less carbon into the atmosphere.  Organize carpools with your neighbors or co-workers to reduce fossil fuel use. Choosing a residence as close as possible to your place of work will reduce both your commute time and energy consumption. Escalators and elevators are convenient, but sometimes they are not necessary, especially if you only have to travel 1 or 2 floors. Not only will taking the stairs save electricity, but you'll also get some exercise in. You also won't have to wait in line.  Escalators and elevators cost money to run. By taking the stairs, you may see lower prices (if you’re at a shopping center) or a higher salary (if you’re at an office building). There are instances where taking escalators or elevators may be necessary, such as if you have an injury, a bad knee, or need to get to the 24th floor.
Question: What is a summary of what this article is about?
Buy products with less packaging. Take a reusable bag with you shopping. Do without disposables. Cut down on electricity use. Use less water. Stop junk mail and paper billing. Consider alternative transportation. Take the stairs.