INPUT ARTICLE: Article: You can make the squares any size you want, but make sure you have enough room to play. Make the squares about 5 feet (1.5 m) per side for most players, although adults might enjoy the challenge from 8 feet (2.4 m) squares. The squares should be numbered clockwise starting with 1. This means the 1 and 4 squares will be diagonal from each other, as will the 2 and 3 squares. Some people use the letters A, B, C, and D instead of numbers, while others use titles of royalty, such as Jack, Queen, King, and Ace. As a "playground game" this game has spawned an incredible amount of local variations over the decades.  If you’re playing by the standard rules, make sure everyone knows what exactly they are before starting. While often one school might have "standard rules" the new kid might think the "standard rules" are something else entirely. If you’re playing by variations, or if the server is allowed to make up rules during the game, make sure everyone is aware of this and agrees to it.     {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/9\/9d\/Play-Four-Square-Step-4-Version-2.jpg\/v4-460px-Play-Four-Square-Step-4-Version-2.jpg","bigUrl":"\/images\/thumb\/9\/9d\/Play-Four-Square-Step-4-Version-2.jpg\/aid36378-v4-728px-Play-Four-Square-Step-4-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/\">Creative Commons<\/a><br>\n<\/p><p><br \/>\n<\/p><\/div>"}  Having everyone on the same page before the game starts will help prevent disputes during the game that could ruin the fun. The players don’t have to stay in their square the entire time, but they should stay close in order to defend their area. The server should bounce the ball once in their own square, then hit the ball so that it goes diagonally to the lowest-ranked square. The receiver can then hit the ball in any direction they choose.  Many people play Four Square so that the 4 square is the highest-ranked square, and therefore the server’s square. If this is the case, the server should stand in the 4 square and hit the ball towards the 1 square. Some people play the game so 1 is the highest-ranked square and 4 is the lowest. In this case, the serve would go from the 1 square towards the 4 square. The serve always goes in the same direction. After the serve, the receiver should allow the ball to bounce one time in their square, then should hit it in whatever direction they choose. If they don’t hit the ball correctly or it goes out of bounds, that is a “fault,” and one fault is allowed per round. If the receiver misses the serve twice in a round, they are eliminated. The round lasts until a player is eliminated. Once the ball is in play, whoever’s square the ball lands in should be the next to hit it. The ball is considered “in play” after someone touches it but before it lands in another square, meaning players can hit the ball in the air. You must hit the ball before it bounces a second time.  If a player hits the line with the ball or hits the ball so it does not land in another player’s square, that player is out.  If a player hits a ball after it has landed in another player’s square, the person who hit the ball is out. This is called “poaching.” Players are not allowed to carry, catch, or hold the ball during play. However, they may repeatedly bounce the ball off of their hands in order to avoid breaking this rule.

SUMMARY: Mark 4 squares on the ground. Number the squares from 1 to 4. Make sure everyone agrees on the rules before you start playing. Have a player stand in each square. Serve the ball from the highest-ranked square to the lowest. Allow one fault for the receiver per round. Take turns hitting the ball after it bounces in your square. Hit the ball with any part of your hand but do not catch it.


INPUT ARTICLE: Article: Let's say you're measuring a stick that falls near 4.2 cm, give or take one millimeter. This means that you know the stick falls almost on 4.2 cm, but that it could actually be just a bit smaller or larger than that measurement, with the error of one millimeter. State the uncertainty like this: 4.2 cm ± 0.1 cm. You can also rewrite this as 4.2 cm ± 1 mm, since 0.1 cm = 1 mm. Measurements that involve a calculation of uncertainty are typically rounded to one or two significant digits. The most important point is that you should round your experimental measurement to the same decimal place as the uncertainty to keep your measurements consistent.  If your experimental measurement is 60 cm, then your uncertainty calculation should be rounded to a whole number as well. For example, the uncertainty for this measurement can be 60 cm ± 2 cm, but not 60 cm ± 2.2 cm. If your experimental measurement is 3.4 cm, then your uncertainty calculation should be rounded to .1 cm. For example, the uncertainty for this measurement can be 3.4 cm ± .1 cm, but not 3.4 cm ± 1 cm. Let's say you're measuring the diameter of a round ball with a ruler. This is tricky because it'll be difficult to say exactly where the outer edges of the ball line up with the ruler since they are curved, not straight. Let's say the ruler can find the measurement to the nearest .1 cm -- this does not mean that you can measure the diameter to this level of precision.  Study the edges of the ball and the ruler to get a sense of how reliably you can measure its diameter. In a standard ruler, the markings at .5 cm show up clearly -- but let's say you can get a little bit closer than that. If it looks like you can get about within .3 cm of an accurate measurement, then your uncertainty is .3 cm. Now, measure the diameter of the ball. Let's say you get about 7.6 cm. Just state the estimated measurement along with the uncertainty. The diameter of the ball is 7.6 cm ± .3 cm. Let's say you're measuring a stack of 10 CD cases that are all the same length. Let's say you want to find the measurement of the thickness of just one CD case. This measurement will be so small that your percentage of uncertainty will be a bit high. But when you measure 10 CD cases stacked together, you can just divide the result and its uncertainty by the number of CD cases to find the thickness of one CD case.  Let's say that you can't get much closer than to .2 cm of measurements by using a ruler. So, your uncertainty is ± .2 cm. Let's say you measured that all of the CD cases stacked together are of a thickness of 22 cm. Now, just divide the measurement and uncertainty by 10, the number of CD cases. 22 cm/10 = 2.2 cm and .2 cm/10 = .02 cm. This means that the thickness of one CD case is 2.20 cm ± .02 cm. To increase the certainty of your measurements, whether you're measuring the length of on object or the amount of time it takes for an object to cross a certain distance, you'll be increasing your chances of getting an accurate measurement if you take several measurements. Finding the average of your multiple measurements will help you get a more accurate picture of the measurement while calculating the uncertainty.

SUMMARY:
State uncertainty in its proper form. Always round the experimental measurement to the same decimal place as the uncertainty. Calculate uncertainty from a single measurement. Calculate uncertainty of a single measurement of multiple objects. Take your measurements multiple times.