4th Grade Math: Understanding Linear Units

Linear Units for 4th Grade

'Linear' means 'straight line' and linear units are used to measure distances, lengths and heights. For instance, you would measure how tall you are, how long a piece of rope is and how far it is to the grocery store in linear units.

Types of Units

Within the metric system, you'll work with meters, which are abbreviated as 'm.' The height of an adult is usually between one and two meters. Centimeters (cm) are used to measure smaller lengths, and 1 m = 100 cm. You'll measure long distances in kilometers (km), each of which is equal to 1,000 meters.

You'll also measure lengths, heights and distances using the customary system. The smallest linear unit in this system is the inch (in), and 12 inches are equal to one foot (ft). Yards (yd) are the next largest unit, and 1 yd = 3 ft. Long distances are measured using miles (mi). One mile is equal to 1,760 yards.

Selecting Units

Once you've learned about the different types of linear units, you'll practice choosing the appropriate unit of measure for solving various problems. Sometimes, you'll just be asked to select the most appropriate unit for measuring different things. In this case, you'll use the largest unit that makes sense. For instance, if the distance between two points is one kilometer or more, you'll use kilometers; however, if it's between one meter and one kilometer, you'll use meters.

Sometimes, you'll be asked to measure different lengths or distances and use this information to answer questions. For example, you might have to measure the length and width of a ribbon to find its area. In problems like this, where the length and width might normally be measured in different units (like feet and inches, respectively), you'll select the unit of measure that makes it easier to solve the problem.

Converting Units

You'll also be asked to convert larger units into smaller units in 4th grade. For instance, how many centimeters do two meters equal? To do conversions like these, you'll multiply the number of larger units by the number of smaller units it takes to make one large unit. Since 100 cm = 1 m, you'd multiply two by 100 to get 200 cm (2 x 100 = 200).

Let's do one more example with customary units. We'll figure out how many feet are in six yards. Since three feet equal one yard, and there are six yards, we'll multiply three by six to get 18 feet (3 x 6 = 18).