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# Length and Time for Nursing School Entrance Exam Study Guide

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Updated on Aug 12, 2011

The practice quiz for this study guide can be found at:

Mathematics for Nursing School Entrance Exam Practice Problems

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.

### Length Conversions

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.

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:
•       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.

### Time Conversions

Word problems involving time typically ask you to determine how long something takes. You might have to add together the amount of time several activities take in order to determine the total amount of time the entire process takes or calculate the elapsed time from the start to the finish of a particular activity.

Adding and subtracting time units is a lot like adding and subtracting length units. You have to make sure that you are adding hours to hours, minutes to minutes, and seconds to seconds. If the given information is in different time units, then you'll have to convert to a common time unit before you can proceed. Use the following conversion ratios:

• To convert minutes to hours:
• To convert hours to minutes:
• To convert seconds to minutes:
• To convert minutes to seconds:
Example: Convert hours to seconds.
 1. Convert hours to minutes: 2. Convert minutes to seconds:
The hours and minutes cancel, giving an answer in seconds.