Taking a math test can be pretty stressful. Even if you know the material, you can still get the problem wrong. Knowing how to go through your math test and check your work can save you from handing in a test full of mistakes that can be avoided. {#blank#}1{#/blank#}

Write it out

    You can also check a math problem by writing everything out on paper. {#blank#}2{#/blank#} Writing out math problems reduces your chances of missing anything to the lowest possible level, which is a common cause of incorrect answers.

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    Make sure your answers work by doing the opposite procedure of what your problem calls for, including the answer you got the first time around. In other words, you would use the opposite of this addition problem—subtraction (减法)—to determine whether or not your answer is the correct one.

Plugging in

    You may find that a variable isn't good enough or have a problem where you have to solve for a variable (变量). {#blank#}4{#/blank#} This is the only real way to assure yourself that the answer you've found is correct.

Check for a reasonable answer

    {#blank#}5{#/blank#} For example, if you get an answer in the millions and you know it should be in the thousands, you've likely misplaced a point. Go back through the work on your paper to make sure all of your formulas and calculations are correct. If everything looks okay, do the problem again and compare the result of the second try to what you've got on the first try.

    A good joke can be the hardest thing to understand when studying a foreign language. As a recent article in The Guardian newspaper noted, “There's more to understanding a joke in a foreign language than understanding vocabulary and grammar.”

    Being able to understand local jokes is often seen as an unbelievable ice-breaker for a language learner eager to form friendships with native speakers. “I always felt that humor was a ceiling that I could never break through,” Hannah Ashley, a public relations account manager in London, who once studied Spanish in Madrid, told The Guardian, “I could never speak to people on the same level as I would speak to a native English speaker. I almost came across as quite a boring person because all I could talk about was facts.”

    In fact, most of the time, jokes are only funny for people who share a cultural background or understand humor in the same way. Chinese-American comedian Joe Wong found this out first-hand. He had achieved huge success in the US, but when he returned to China in 2008 for his first live show in Beijing, he discovered that people didn't think his. Chinese jokes were as funny as his English ones.

    In Australia, meanwhile many foreigners find understanding jokes about sports to be the biggest headache. “The hardest jokes are related to rugby because I know nothing about rugby,” said Melody Cao, who was once a student in Australia. “When I heard jokes I didn't get, I just laughed along.”

    In the other two major English-speaking countries, the sense of humor is also different. British comedian Simon Pegg believes that while British people use irony (反话)—basically, saying something they don't mean to make a joke—every day, people in the US don't see the point of using it so often. “British jokes tend to be more subtle and dark, while American jokes are more obvious with their meanings, a bit like Americans themselves,” he wrote in The Guardian.

    Most American students go to traditional public schools. There are about 88,000 public schools all over the US. Some students attend about 3,000 independent public schools called charter schools.

    Charter schools are self­governing. Private companies operate some charter schools. They are similar in some ways to traditional public schools. They receive tax just as other public schools do. Charter schools must prove to local or state governments that their students are learning. These governments provide the schools with the agreement called a charter that permits them to operate.

    Charter schools are different because they do not have to obey most laws governing traditional public schools. Local, state or federal governments cannot tell them what to teach. Each school can choose its own goals and decide the ways it wants to reach them. Class size is usually smaller than in traditional public schools.

    Governments strongly support charter schools as a way to re­organize public schools that are failing to educate students. But some education agencies and unions oppose charter schools. One teachers' union has just made public the results of the first national study comparing the progress of students in traditional schools and charter schools.

    The American Federation of Teachers criticized the government's delay in releasing the results of the study, which is called the National Assessment of Educational Progress. Union education experts say the study shows that charter school students performed worse in math and reading tests than students in regular public schools.

    Some experts say the study is not a fair look at charter schools because students in those schools have more problems than students in traditional schools. Other education experts say the study results should make charter school officials demand more student progress.

    My father was attached to gardening by birth. One of my earliest memories is following Dad barefoot around in the garden with both hands blackened from digging in the soil. The garden was a wonderland full of possibilities.

    As Dad grew older, he still loved gardening. Even when he was diagnosed with cancer, he still planted all sorts of plants. Sometimes, I would come over to visit, and we would walk together in the garden. But then, something changed. Like the weeds that took over his garden, the cancer grew rapidly in Dad, and the doctor gave up. I stayed with Dad twenty-four hours a day and I found myself in all kinds of uncomfortable situations with Dad until I promised to care for the garden.

    Though I had heard the words of the doctor, what really made me believe that Dad was dying was the state of his garden. That year, he only planted tomatoes. Too tired to weed them, he simply tied them with strong strings to the fence and let them be. It made me sad to see them ignored, so I would come over and water them once in a while, and remove the weeds. I still remember the day I picked the last tomato from the vine(藤). That day was one of the saddest I had ever experienced in my life.

    Three years ago, I decided to plant my own garden. I decided I would start out with just a few tomatoes. That morning when I moved to the garden, something caught the corner of my eye and I had to smile. It was my eight-year-old son Nathan, standing barefoot in the soil, happily playing in soil.

    US Space Agency Returns to Mars with InSight Lander

    The American space agency's lander InSight is to arrive on Mars at the end of November, 2018. Unlike NASA's Curiosity rover, InSight will not move across the planet's surface. Instead it will become the first spacecraft (航天器) used only for exploring underground. It will study the geography of Mars, searching for signs of Martian (火星的) quakes.

    InSight is a project of U.S. and Europe. It is 6 meters long and 1.5 meters wide. It weighs 360kilograms. InSight's 1 .8 -meter robotic arm will put two experiments in place. Both are designed toexplore underground of Mars to learn about the inside.

    Bruce Banerdt is the lead scientist for InSight. He viewed the spacecraft as a robot that can take care of itself. "It's got its own brain. It's got an arm. It can listen and feel things. It pulls its own power out of the sun," he noted.

    Thomas Zurbuchen, one of the heads in NASA, said the results of the InSight project could "change the way we think about the inside of our earth." But, first, InSight will have to land on Mars undamaged. Since Mars exploration started in the 1960s, only about 40 percent of the explorations have succeeded.

    Tom Hoffman is InSight's project manager. He said earlier successes do not lessen the concerns for each new exploration. "That we ve done it before doesn't mean we're not nervous and excited about doing it again," he said.

    InSight will enter the Martian atmosphere (大气层) traveling at 19,800 kilometers an hour. It will slow for landing on a wide flat area on Mars. If all goes well, InSight could carry out its experiments in about 10 weeks. The InSight project is expected to continue for one Martian year, about two years on Earth.

Inventor, physicist, surveyor, astronomer, biologist, artist... Robert Hooke was all these and more. Some say he was the greatest experimental scientist of the 17th century. In the course of his work, he cooperated with famous men of science like Isaac Newton, and the great architect, Christopher Wren.

Hooke's early education began at home, under the guidance of his father. He entered Westminster School at the age of 13, and from there went to Oxford, where he came in contact with some of the best scientists in England. Hooke impressed them with his skills at designing experiments and inventing instruments. In 1662, at the age of 28, he was named Curator of Experiments at the newly formed Royal Society of London — meaning that he was responsible for demonstrating new experiments at the society's weekly meeting. Hooke accepted the job, even though he knew that the society had no money to pay him!

Watching living things through a microscope was one of his favourite pastimes. He invented a compound microscope for this purpose. One day while observing a cork under a microscope, he saw honeycomb­like structures. There were cells — the smallest units of life. In fact, it was Hooke who invented the term "cell" as the box­like cells of the cork reminded him of the cells of a monastery．

Another achievement of Hooke's was his book Micrographia, which introduced the enormous potential of the microscope. It contains fascinating drawings of the thing he saw under the microscope. The book also includes, among other things, ideas on gravity, light and burning that may have helped scientists like Newton when they were developing their own theories on these phenomena.

Hooke made a valuable contribution to astronomy too. A crater on the moon is named after him in honour of his services to this branch of science.