The Basics of Math—Made Clear

    Basic Math introduces students to the basic concepts of mathematics, as well as the fundamentals of more tricky areas. These 30 fantastic lectures are designed to provide students with an understanding of arithmetic and to prepare them for Algebra(代数) and beyond.

    The lessons in Basic Math cover every basic aspect of arithmetic. They also look into exponents(指数), the order of operations, and square roots. In addition to learning how to perform various mathematical operations, students discover why these operations work, how a particular mathematical topic relates to other branches of mathematics, and how these operations can be used practically.

    Basic Math starts from the relatively easier concepts and gradually moves on to the more troublesome ones, so as to allow for steady and sure understanding of the material by students. The lectures offer students the chance to “make sense” of mathematical knowledge that may have seemed so frightening. They also help students prepare for college mathematics and overcome their anxiety about this amazing—and completely understandable—field of study.

    By the conclusion of the course, students will have improved their understanding of basic math. They will be able to clear away the mystery(神秘性) of mathematics and face their studies with more confidence than they ever imagined. In addition, they will strengthen their ability to accept new and exciting mathematical challenges.

    Professor H. Siegel, honored by Kentucky Educational Television as “the best math teacher in America,” is a devoted teacher and has a gift for explaining mathematical concepts in ways that make them seem clear and obvious. From the basic concrete ideas to the more abstract problems, he is master in making math lectures learner-friendlier and less scary.

    With a PhD in Mathematics Education from Georgia State University, Dr. Siegel teaches mathematics at Central Arizona College. His courses include various make-up classes and a number of lectures for future primary school teachers.

    If the course fails to provide complete satisfaction to you, you can easily exchange it for any other course that we offer. Or you can get your money back.

    Emily and Zach are confused! Their parents told them they could choose between Massachusetts and Arizona for their vacation this summer.

    Emily has always wanted to visit Boston, the capital of Massachusetts. Zach and she both agree that walking along the Freedom Trail would enable them to see Boston's most famous places of historic interest, like the site of the school Ben Franklin attended and the Old State House. If Emily and Zach went to Massachusetts, they could spend a few days at the beaches on Cape Cod. Emily loves body boarding, and Zach is great at body surfing. They both enjoy building sandcastles .

    Zach finds learning about Native Americans wonderful and has always wanted to travel along the Apache Trail in Arizona. This mountain highway passes Native American ruins in Tonto National Forest. Emily is not as interested in traveling along this trail as Zach, but they both would like to visit Phoenix, the capital, and then travel to Grand Canyon National Park and Meteor Crater (陨石坑). Zach learned in science class that Meteor Crater is a hole over 4,000 feet wide and 520 feet deep that was created when a huge object from space fell to Earth. The object went so deep that it has never been found. Zach would really like to try to discover it. But Emily thinks if experienced scientists and researchers cannot find it, Zach might as well not even bother (费工夫) to try.

    The only drawback for Zach and Emily if they choose Arizona would be the heat. It is very hot and dry in this southwestern state. Massachusetts, on the other hand, is in the northeastern United States. Here Zach and Emily and their parents could enjoy mild (温和的) temperatures. Their parents love hot weather, but Zach and Emily do not really like to sweat.

    How will they ever decide to which state they should travel? If only they could take two trips!

Following the old saying of "early to bed and early to rise" I used to go to bed at 10 pm and get up early at 6 am to get ready for school. But that day, as it was cloudy, I continued to sleep for long, thinking it to be the early hours of the day.

Suddenly, I heard a loud voice which startled me up and made me sit upright. It was my mother's voice who was knocking and shouting, "Get up honey. It's 6:45 am already! You are getting late for school!" As it was a cloudy day, I hadn't realized that it was almost 7 and continued dozing for long!

But thank fully that day our pick-up person who generally used to come at 6:50 am got late due to the showers and arrived just in the nick of time when I was ready. By the time we reached school it was a quarter to eight and the drizzle from previous night had finally stopped. I entered the classroom fearing the teacher's anger, but saw only a few students had made it to school. Therefore, the principal declared a holiday. "Hurray!" We all cheered in a chorus at the unexpected holiday and decided to walk back home.

    As it had been continuously drizzling since the previous night there was water all over the place and the roads were impassable. Just then, at a distance my sister and I saw little kids playing in knee-deep water in the streets which touched the play button in us. We quickly approached them and merrily jumped and hopped in the pool of water with them. With shoes in our hands we continued parading on the muddy streets. We were thrilled and our hearts were filled with joy at the sight of the green and fresh leaves on the trees; the frogs drew our attention as we tried to catch butterflies.

    We finally reached home busily playing and laughing with mud-spattered uniforms and shoes. We hurriedly changed our outfits, washed up and sat watching TV with a bowl of hot soup! No doubt, I thoroughly enjoyed this day and secretly prayed for many such days in the future! To this day when it pours, the memories of that eventful rainy day bring a smile on my face!

    Elephants have impressed us for centuries. They are big, clever, and sociable. But what if someone told you that they may also hold the key to fighting cancer (癌症)?

    People have been wondering why elephants do not develop cancer, even though they have lifespans (寿命) that are similar to humans, living for around 50 to 70 years.

    Now scientists believe they know why. A team at the University of Chicago, US has found that elephants carry a large number of genes that stop tumors (肿瘤) from developing. To be precise, they found 20 copies of an anti­tumor gene called TP53 in elephants. Most other species, including humans, only carry one copy.

    According to the research, which was recently published on the online science network BioRxiv, the extra copies of the gene improved the animal's sensitivity to DNA damage. This lets the cells quickly kill themselves when damaged before they can go on to form deadly tumors.

    “An increased risk of developing cancer has stood in the way of the evolution of large body sizes in many animals，” study author Dr. Vincent Lynch told The Guardian. If every living cell (细胞) has the same chance of becoming cancerous, large creatures with long lifespans like whales and elephants should have a greater risk of developing cancer than humans and mice do. But across species, the risk of cancer does not show a connection with body mass.

    This_phenomenon was found by Oxford University scientist Richard Peto in the 1970s and later named "Peto's paradox". Evolutionary (进化的) biologists believe it results from larger animals using protection that many smaller animals do not. In the elephant's case, the making of TP53 is nature's way of keeping this species alive.

    The study also found that when the same genes were brought to life in mice, they had the same cancer resistance (抵抗) as elephants. This means researchers could use the discovery to develop new treatments that can help stop cancers from spreading or even developing in the first place.

    "Nature has already figured out how to prevent cancer, " said Joshua Schiffman, an oncologist at the School of Medicine, University of Utah, US.

    “It's up to us to learn how different animals tackle (处理) the problem so we can use those strategies to prevent cancer in people.”

    Although it's great to spend vacations seeing the world with family, friends, or a lover, traveling alone can also be completely incredible. A solo adventure has the potential to be life-changing. Here are some reasons you should travel alone at least once.

    If you enjoy meeting new friends, here's your chance; you will likely find some when traveling alone, Since you won't be focused on talking to anyone you know, you'll be more likely to strike up conversations with strangers. Meeting people from different backgrounds opens our minds, expands our world, and can inspire us a lot. You may meet some amazing locals or other adventurers like yourself; either way you're bound to make some new friends during your journey.

    A trip alone can ignite your creativity. Spending time alone with an open mind can be exactly what you need for your imagination to soar. Your enthusiasm and passion for life may sky-rocket from your awesome adventure.

    When traveling with a partner or a group, every idea can be bounced off someone else. When you travel alone, you will learn to be decisive; you will be making every decision alone. From where to eat, to what time to wake up, to what sights to see, and which airline to use, traveling solo forces you to rely on yours truly. As you realize you can make good choices without help from others, you will likely trust your instincts more, and this new found self-assurance and confidence will be helpful in many areas of your life.

    Plants are living things. So can they feel pain? Plants don't feel pain the same way animals and people do, says Anke Steppuhn. She is a scientist at the Free University of Berlin in Germany. "What we define as pain usually has to do with a nervous system," Steppuhn explains. When you put your hand too close to a hot stove, nerve cells send a signal to your brain. Your brain decodes (解码) that signal as pain. This causes you to pull your hand away before any serious damage is done.

    Plants don't have nerves or brains, so they can't feel pain like we do. "But plants do recognize when something is hurting them," Steppuhn says. Because they are rooted to the ground, they can't escape a dangerous situation. So they need other ways of fighting back.

    The biggest threat to a plant's life is getting eaten. Some plants grow sharp little hairs. Other plants produce bad-tasting or even harmful chemicals. These force an attacker to abandon its meal. A plant called bittersweet nightshade does something even smarter, Steppuhn found. When a slug (蛞蝓) chews holes in a nightshade' s leaf, liquid begins dripping (滴) around the wound. It is almost as if the plant were bleeding. The liquid is sugary nectar (花蜜), and it happens to be a favorite food of ants. In their effort to collect the nectar, the ants swarm (蜂拥而至) all over the injured plant. They will attack anything that stands in their way. That includes the slug that damaged the plant in the first place. It's a very clever trick. Whenever a slug attacks a plant, the plant calls an army of ants to kill the slug.

    Nectar isn't the only way plants attract bodyguards. They also release certain chemicals into the air when they are being eaten. People usually can't detect these smells. But wasps (黄蜂) can. When a wasp detects this cry for help, it races to the scene of the crime. If it finds the right kind of insect chewing down on the plant, the wasp will interrupt the attacker's meal. It will do this by laying eggs inside the insect's body!