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1.2 Rounding & Calculators

1.2 Rounding & Calculators
  • Math Help

    In Section 1.1 Math Help (page 5), we suggested that there are two area formulas that are useful to memorize.

    (Rectangle: A = bh) (Circle: A = pi times r squared)

    When you need to find the area of other geometric shapes, you can usually use one or both of these formulas to derive a formula for the area of the other shape. For example, to find the area of a right triangle whose base is 4 feet and whose height is 3 feet, you can imagine that the triangle is half of a rectangle.

    Because the area of the rectangle is A = bh, it follows that the area of the triangle is

    A = 1/2 bh = 1/2 (4ft) x (3ft) = 6ft squared

    Remember to always check your calculations for correct units. In the above product,

    • 1/2 has no units. Like π, it is a ratio. In this case, the ratio of the area of a triangle to the area of its corresponding rectangle.
    • 4 is the base. The base has feet as its units.
    • 3 is the height. The height has feet as its units.
    • 6 is the area. The area has square feet as its units.
  • Consumer Suggestion

    Are you familiar with the Vietnam Veterans Memorial in Washington, D.C.? You can find information about the Wall at The Vietnam Veterans' Memorial Wall Page. At this site, you can search for fallen soldiers of the Vietnam War who were from your hometown.

    Did you know there is a replica of the Wall that travels the United States? Find out more information by visiting the Vietnam Traveling Memorial Wall website.

  • Checkpoint Solution

    There are several ways to estimate the average number of characters in the names of the men and women who died in the Vietnam War. A straightforward way is to assume that the people who died have the same types of names as people in a typical metropolitan phone book. Having done that, you could randomly select 50 or 60 names and count the characters.

    When we did this, we found the average number of letters in last names to be 7 and the average number of letters in first names to be 5. So, one estimate for the number of characters is

    7 + 1 + 1 + 5 + 1 + 1 = 16

    Remember, that this number is an estimate. Most of the names on the memorial would have a different number of characters, as in GARY W ERICSON, which has 14 characters counting the two spaces.

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