INPUT ARTICLE: Article: "Pump filters" may be your cheapest option in this category, but can be slow and tedious. For long trips, look into "gravity filters," which are typically a pair of bags connected by a hose. The bag with the filter is filled with water, then hung up to let the water drain through the filter into the clean bag. This is a fast, convenient option that doesn't require you to carry around a supply of disposable filters. These filters do not protect against viruses, but they are effective against bacteria. Not all wilderness areas require protection against viruses, however, especially in the US. Check your regional disease control center or a tourist information center for more information on the risks in your region. Tablets are slow but cheap, and are effective against most bacteria and viruses. Tablets come in two common types: Iodine tablets should be left in the water for at least 30 minutes. They are sometimes sold with a companion tablet for hiding the iodine taste. Pregnant women and people with thyroid conditions should not use this method, and no one should use it as their main source of water for more than a few weeks. Chlorine dioxide tablets normally have a 30 minute wait time. Unlike iodine, they are effective in areas contaminated by the bacterium Cryptosporidium but only if you wait 4 hours before drinking. Ultraviolet light lamps can kill bacteria and viruses, but only if the water is clear and the light is applied for long enough. Different UV lamps or light pens have different intensities, so follow the manufacturer's instructions. This is an extremely effective method of killing pathogens, as long as you let the water boil for at least one minute. It may not be convenient to boil water several times a day, but be aware that you won't need additional filtration if you're already boiling water for your evening meal or morning coffee. At high elevations, boil the water for at least three minutes, since the water will boil at a lower temperature in the thin air. The high temperature, not the boiling action itself, is responsible for killing bacteria and viruses. Plastic bottles are only designed to be filled an used once, since the plastic can break down over time, adding potentially harmful chemicals to the water and even harboring bacteria. Even aluminum bottles often have an inner plastic coating, and are not dishwasher safe, making them difficult to clean. If you're lucky enough to find a mountain spring bubbling from the rocks, it's usually safe to drink directly from it but this does not apply even a couple feet (0.6 m) away. This is not a foolproof rule, and may be dangerous in agricultural regions, areas with historic mining, or lower-elevation areas near population centers.

SUMMARY: Consider a physical filter. Learn about chemical disinfection. Try UV light treatment. Boil water. Use stainless steel water bottles. Drink straight from the spring source.

In one sentence, describe what the following article is about: A fraction is always written with one number on top of a line and another number underneath that line. The numerator of a fraction is the top number. It is the "part" of the "whole" that you are talking about. For example, in the fraction , 1 is the numerator. The fraction indicates one part of a whole that has four parts. The denominator is the bottom number of the fraction and represents the "whole". It is the number of parts the whole is divided into. To remember the denominator think "down"-ominator. For example, in the fraction , 4 is the denominator. This whole has been divided into four equal parts. A fraction is considered improper if the numerator (the top number) is larger than the denominator (the bottom number). When working with fractions, you never want to write a final solution as an improper fraction. Always remember to simplify it into a mixed or whole number. Some examples of improper fractions: 10/3, 9/4, 15/3, 25/5. into mixed or whole numbers. Some fractions can simply be divided into a whole number, while others will not divide evenly. Numbers that don't divide evenly must be rewritten as a mixed number. To simplify an improper fraction, first divide the numerator by the denominator. For example, for the fraction 10/3, divide 10 by 3. 3 goes into 10 three times (3 x 3 = 9), but there will be a remainder of 1. Write the remainder as a fraction of the original denominator. With a remainder of 1 the fraction of the mixed number will be 1/3. The mixed number of 10/3 is 31/3. Note, not all improper fractions will be mixed numbers; some will simplify into whole numbers. For example: 25/5 simplifies to 5. You might be surprised to find that you use fractions on a pretty regular basis throughout your day. You may know fractions by a different name, decimals. Do you ever trade or share food with your friends at lunch? Maybe you trade half of your chips for half a dessert. These are fractions! Do you ever help your parents with baking? Measuring cups use fractions. A recipe may call for teaspoon of vanilla or 2/3 of a cup of flour. Pay attention throughout your day and see how many times you use fractions without even realizing it.
Summary: Identify the numerator. Identify the denominator. Recognize an improper fraction. Simplify improper fractions Identify the use of fractions in your daily life.

INPUT ARTICLE: Article: Click the "Mail" link next to the picture of an envelope in the top right corner of the main Yahoo.com page. Click the "Compose" button on the left side of the screen to start a new email. Click the "Inbox" button on the left side of the screen to browse a list of the emails you have been sent. Note that, by default, your Yahoo email account displays your inbox as soon as you log in. Click on an email you've been sent in your inbox. Pick a reply option with the buttons at the top left of the email. You can reply normally (curving arrow pointing left), reply to all (multiple curving arrows; used when you are one of multiple recipients), or forward the message (straight arrow pointing right). In your email inbox, click the icon that looks like an address book in the top left. This will bring you to a list of your online contacts. To add a new contact to the list (which will be blank if you've just created an account), click "New Contact" in the top left. You can also choose to import contacts from a social media profile by clicking one of the buttons in the center of the screen and following the prompts. Having someone in your list of contacts gives you several benefits. For instance, you don't have to remember this person's email address you can just start typing his or her name in the "To:" field of your email and it will display automatically. This is especially useful when you need to send a single email to many recipients.

SUMMARY:
Access your email account. Send new emails: View emails you've received. Reply to emails. View your contacts.