Length and Time for Nursing School Entrance Exam Study Guide
The practice quiz for this study guide can be found at:
The United States uses the English system to measure length; however, most other countries use the metric system, which is also prevalent in scientific use in the United States. The English system requires knowing many different equivalences, but you're probably used to dealing with these equivalences on a daily basis. Mathematically, however, it's simpler to work in metric units because their equivalences are all multiples of 10. The meter is the basic unit of length, with all other length units defined in terms of the meter.
Math questions on standardized tests, especially geometry word problems, may require conversions within a particular system. An easy way to convert from one unit of measurement to another is to multiply by an equivalence ratio.
Example: Convert 3 yards to feet.
Multiply 3 yards by the ratio . Notice that we chose rather than because the yards cancel during the multiplication:
Example: Convert 31 inches to feet and inches.
|1. First, multiply 31 inches by the ratio :|
|2. Then change the portion to inches:|
|3. Thus, 31 inches is equivalent to both ft. and 2 feet 7 inches.|
Addition and Subtraction with Length Units
Finding the perimeter of a figure may require adding lengths of different units.
Example: Find the perimeter of the figure at right.
To add the lengths, add each column of length units separately:
Since 27 inches is more than 1 foot, the total of 16 ft. 27 in. must be simplified:
- Convert 27 inches to feet and inches:
- Add: 16 ft.
Thus, the perimeter is 18 feet 3 inches.
Finding the length of a line segment may require subtracting lengths of different units.
Example: Find the length of line segment AB to the right.
To subtract the lengths, subtract each column of length units separately, starting with the rightmost column.
Warning: You can't subtract 8 inches from 3 inches because 8 is larger than 3! As in regular subtraction, you have to borrow 1 from the column on the left. However, borrowing 1 ft. is the same as borrowing 12 inches; adding the borrowed 12 inches to the 3 inches gives 15 inches. Thus:
- Thus, the length of is 5 feet 7 inches.
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