The formula is A=(r2){\displaystyle A=\pi (r^{2})} where r{\displaystyle r} equals the length of the circle's radius. Pizza sizes are measured by their diameter. To find the length of the radius, you have to divide the diameter in half. For example, if you are ordering a 20 inch pizza, calculate 202=10{\displaystyle 20\div 2=10}. So the radius of the pizza is 10 inches. Remember to substitute for the variable r{\displaystyle r}. For example, if the radius is 10 inches, your formula will look like this: A=(102){\displaystyle A=\pi (10^{2})}. To square a number, multiply it by itself. For example, if the radius is 10 inches, you would calculate 1010=100{\displaystyle 10 imes 10=100}, so your formula will now look like this: A=(100){\displaystyle A=\pi (100)}. You can use a calculator, or use 3.14 for {\displaystyle \pi }. The result will give you the area, in square inches, of your pizza. For example:A=(100){\displaystyle A=\pi (100)}A=3.14(100){\displaystyle A=3.14(100)}A=314{\displaystyle A=314}So, the area of a 20-inch round pizza is 314 square inches. This will give you the cost per square inch of the pizza. For example, if a pizza costs $32 and has an area of 314 square inches, you would calculate 32314=.101{\displaystyle 32\div 314=.101}. So, the cost per square inch of pizza is about .10, or 10 cents. When comparing value, the best value is the pizza with the lowest cost per square inch. This is only true, however, when comparing pizzas with the same toppings. A cheese pizza is likely to be cheaper per square inch than a pizza with several toppings, but that doesn't necessarily make it the best value.
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One-sentence summary -- Set up the formula for the area of a circle. Divide the size of the pizza in half. Plug the length of the radius into the formula. Square the length of the radius. Multiply by {\displaystyle \pi }. Divide the price of the pizza by the number of square inches. Compare the value of pizzas.

If you have a significant amount of paint left, you can return it to the original can; remember, however, that the amount you return to the can has already been thinned, meaning the next time you use it, you may need to adjust the amount of thinner used. Epoxy paints and paints that use a catalyst (two-part paints) cannot be returned to the original can; they must be used entirely or disposed of properly once mixed. Wipe off/out any excess paint. If there is too much paint left in the cup or the spray assembly, you may have to repeat this step a few times. Do this as soon as the paint job has dried; leaving the tape on the surface for an extended period will allow the adhesive to set, making it difficult to remove.
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One-sentence summary -- Pour out the unused paint. Rinse the siphon tube and cup with thinner. Fill the spray cup about 1/4 of the way with paint thinner, slosh it around, and spray it through the sprayer until it comes out clear. Remove all masking tape and paper from your work area.

If you're thinking about suicide, seek immediate help from a mental healthcare professional. There are options available to you 24 hours per day, 7 days a week. Even if your instincts are telling you that you do not wish to call so much attention to yourself, suicidal impulses are very serious, and you should never hesitate to reach out for help. You can call anonymously. If you are in the US, please call 911 or 800-273-TALK (8255), the National Suicide Prevention Hotline, or go to the nearest hospital Emergency Room. If you're in the UK, you can call Samaritans at 116 123 or PAPYRUS at 0800 068 41 41 (if you are a teen or a young adult). Other centers can be found on the International Association for Suicide Prevention website. If you're using the help line for support and still want to die, tell them you do need to go to the hospital. If you are not using a help line, call the Emergency Services or a person you trust and tell them that you want to kill yourself. Ask them to help you get to a hospital, or go there directly yourself. Even better, get someone to drive you. It is hard to drive safely under these conditions. Although Step 1 is the right first step in any situation where you are thinking of killing yourself, it may not feel right for everyone. In this case, you should tell someone you trust that you're having suicidal thoughts immediately. If you are alone, call a friend, a family member, a neighbor, a doctor, chat to someone online, or do whatever you can to not be alone during this time. Talk with someone on the phone and have someone come over to stay with you so that you are not alone. If you have to wait for someone to come over or have to wait at the hospital, sit down and breathe slowly. Control your breathing by timing it, taking maybe twenty breaths a minute. Do anything else you can to distract yourself, knowing that help is on the way. Do not use drugs or alcohol during this time as it can impair your thinking. It can also lead to making your feelings worse, not better. If you feel like you need to cause yourself some pain, hold an ice cube in your hand for 1 minute without letting go (this is a technique used in child-birthing classes to help women practice getting through the pain of pregnancy). The discomfort can be grounding without causing any harm. Listen to your favorite band's album. Watch a funny TV show. Even if these do not make you feel better, they may distract you from your feelings while you wait for help to arrive.
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One-sentence summary -- Get professional help immediately. Contact or go to a hospital. Talk to someone you trust about your thoughts immediately. Wait for help.

When your teacher says a test is coming up, avoid cramming the night before. Plan to study for about 60 minutes each day to brush up for the test. Re-read the book chapters you'll be tested on and look over your relevant in-class notes to see what mistakes to avoid. If you have time, you could even test yourself with flash cards or form an impromptu study group with your friends. If you find that you've forgotten some of the math lessons or are still struggling with a tricky concept, ask for help! The teacher will appreciate your earnestness and won't mind answering your questions. Study groups are a great way to prepare for a test and a useful method for improving your math abilities in general. They let you and your peers ask each other questions about topics that confuse you and review material that's going to appear on an upcoming test or exam. Try studying with flash cards, or working difficult problems together. Keep focused during group study time! If it turns into a social hour, your math skills won't get any stronger. If people start joking around or lose focus, say something like, "Hey guys, I'm glad we're having a good time, but let's keep focused on the math we came here to study." Many people are anxious or nervous during math tests. Feeling this way can diminish your performance, unfortunately, and can lower your math grade. So, take a deep breath before you go into the classroom to stay calm. If you feel yourself tensing up during the test, stand up, stretch your legs, and take a 23 minute break to calm down. Also make sure you get a good night's sleep and eat a full, healthy meal before going in for a math test.
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One-sentence summary --
Plan to study for 34 days in advance of an upcoming text or exam. Study in a group of peers to help each other improve at math. Stay calm and focused during tests to do well on them.