Scientists understand the Celsius scale as derived from the Kelvin scale. Though the gaps between Celsius and Kelvin are even larger than the gaps between Celsius and Fahrenheit, one thing that Celsius and Kelvin have in common is that they rise at the same rate. Whereas the ratio for Celsius to Fahrenheit is 1:1.8, the ratio for Celsius to Kelvin  is 1:1. If it seems odd that freezing for Kelvin would be such a high number — 273.15 — it's because the Kelvin scale is based around absolute zero, which is 0K. Though 0°C is the freezing temperature of water, scientists actually understand 0°C as 273.15K. Since the two scales rise at the same rate, then converting Celsius to Kelvin always means simply adding 273.15. For example, if you're working with the temperature 30°C, just add 273.15 to that. 30 + 273.15 = 303.15K. Here's a rough scale so you can test whether your answer makes sense. Note that the Celsius and Kelvin scales increase at the same rate, so the two numbers are always exactly 273.15 apart.  If you start with an integer value of degrees Celsius, your result in kelvins will end in the decimal .15. The lowest possible temperature is -273.15ºC = 0 kelvins. If your result involves negative kelvins, you either made a math mistake or the problem uses impossible values.  ºCelsius kelvins    -100    173.15     -50    223.15     0    273.15     50    323.15     100    373.15     200    473.15     500    773.15

Summary: Understand the scales. Add 273.15 to your Celsius temperature. Check your answer.


Not getting enough sleep definitely affects mood swings. It can be hard to get enough sleep sometimes when your friends want to talk or hang out at night, but remember that it's important to get enough sleep so that you can feel your best.  Of course you don't want to miss out on hanging out with your friends, but don't make it an every night thing. It's suggested that teens get 8 to 10 hours of sleep each night. Make sure you eat regularly and eat the right foods. This means staying away from loads of sugar and including a balance of carbohydrates, protein, fruits, and veggies every day. If you skip a meal or don't eat enough, notice if this affects your mood. Make sure you're eating regularly to avoid mood swings related to hunger.  A diet that is high in saturated fats and caloric levels may lead to depression.  Those who consume more water, fiber, ascorbic acid, tryptophan, magnesium and selenium have better moods overall. Diets that are heavy on legumes, fruits and vegetables, such as the Mediterranean diet, meet these criteria.  Add folic acid, which can be found in leafy greens and beans. Caffeine can interrupt your sleep. It can also cause nervousness, anxiety, shakiness, and dehydration. If you experience moodiness frequently, remove caffeine and see if it helps. It may be that one thing that pushes you over the edge.  The effects of caffeine are typically felt within five to 10 minutes and may last from one to five hours. Aftereffects may last for up to 24 hours.  A strong dose of caffeine may lead to jitteriness, increased heart rate, irritability, and restlessness. A strong dose is between 150-400 mg. (A coffee contains roughly 150 mg per 12 oz.; an energy drink is in excess of 100 mg per 12 oz; a diet coke is around 46mg per 12oz (or one can).)  If you do consume caffeine, try not to exceed 50-150 mg, or about one 12oz cup of coffee. Exercise can help you improve your mood, increase self-esteem, and improve sleep. When you exercise, your body releases endorphins, which help you get into a better mood and de-stress. Exercise is good for physical and emotional health.  It's recommended that teens get one hour of exercise almost every day.  Maybe you hate sports, but that doesn't mean you can't exercise. Walk the dog, jump on the trampoline, go in-line skating, or go dancing. Sometimes you may want to be left alone and avoid people altogether, and that's okay. But it's also important to spend time with friends. Maybe you have one friend you can tell everything to; talk to her and let her know how you're feeling. Talk to a trusted adult, such as a parent, guidance counselor, or coach. Talk to your best friend, or maybe say hello to your crush. Sometimes mood swings are just mood swings, while other times they can indicate a more serious disorder. If your mood swings are more intense than other girls', talk to a trusted adult about seeing a mental health professional to explore other causes. If you've noticed other symptoms, such as racing thoughts, incoherence, disjointed thoughts, or periods of excessive energy, this can indicate symptoms of other more serious disorders. Talk to an adult and a mental health professional.

Summary: Get some sleep. Watch how hunger affects your mood. Avoid caffeine. Get some exercise. Talk to someone. Understand that mood swings can indicate more serious disorders.


The nines times table has the great trick that the digits of your answer always add up to 9. This works as follows:  9 x 1 = 09. 0 + 9 = 9 9 x 2 = 18. 1 + 8 = 9 9 x 3 = 27. 2 + 7 = 9 9 x 4 = 36. 3 + 6 = 9. etc. For example, the tens digit of 9 x 3 will be 3-1, or 2. Therefore the answer to 9 x 3 should begin with 2. Use this pattern to help keep you on track: if you find that your answer to 9 x 2 begins with a 4 (and not a 1), you know you have gone astray somewhere.

Summary: Remember that the digits of your answer should all add up to 9. Remember that the tens digit of 9 x some number will be some number minus one.


If you have an infection of the skin or nails that affects only a small area and does not cause much irritation, you may consider trying over-the-counter treatments before seeing your doctor. Buy topical antifungal treatments at your local pharmacy or drugstore. Keep in mind that these treatments often work better on skin than nails. Make sure your hands are as clean as possible before touching the affected area. Run warm water over hands and clean them with antibacterial soap. This can help prevent you from irritating your skin even further. Washing your hands after you touch the affected area can help prevent the infection spreading elsewhere. Most topical antifungal treatments need to be applied directly to the infected area. Refer to the instructions on the label of your treatment to ensure that you use it correctly. In most cases, place a small amount of cream or ointment on your fingers and rub it directly onto the infected area. Do not use topical treatments more than the product’s label directs you to, unless your doctor has told you otherwise. You want to make sure the treatment absorbs into your skin or nail rather than any fabric around your foot. Avoid taking a bath or shower immediately after applying the treatment. If the cream or ointment you’re using gives you a rash or seems to make your condition worse, stop using it immediately. Contact your doctor if the side effects don’t go away in a few days. If your symptoms don’t improve within 2 weeks, seek medical attention. Seek medical attention immediately if your infection spreads or starts to cause greater irritation. In most cases, your doctor will prescribe stronger antifungal medication. Use this prescription medication only as directed.


Summary: Purchase over-the-counter anti-fungal cream and ointments. Wash your hands before and after using the treatment. Follow the instructions on the treatment's label. Let the cream or ointment dry before putting on socks or shoes. Stop using the treatment if you have adverse side effects. See your doctor if over-the-counter remedies don’t help.