For high-school math Common Core Standards, quantity focuses on the student's ability to reason qualitatively and use units to solve problems. For example, the student should be able to do the following:

• Read a multistep word problem and use units to figure out the solution. In other words, in word problems that contain values in different units (for example, distance in meters and kilometers), the student should be able to determine the most efficient conversion to use to convert all distance measurements to kilometers or meters and to solve the problem.

• Determine which quantities to use for descriptive modeling, for example, which units are most appropriate for solving a problem that asks for the time required to fill a swimming pool with water.

• Choose a level of accuracy based on measurement limitations; in other words, how precise should you be when rounding numbers up or down? For example, if you fill your gas tank with 10.275 gallons of gas priced at \$3.339 dollars per gallon, the cost is \$34.308225, but because you're paying with dollars and cents, rounding up to the nearest hundredth makes sense; the cost is \$34.31.

• Choose and interpret the origin (the point from which data is measured) and scale (the tick marks along the X and Y axes) in graphic representations of data.

Challenge your child to solve real-world problems that involve several steps and various units of measure and show you how she figured it out.

For example, suppose Aunt Sally is meeting you for lunch. The restaurant is 5 miles from her house and 15 miles from yours. Aunt Sally is leaving her home at 11:30 and will be driving an average of 30 miles an hour. You'll be driving an average of 45 miles an hour. When do you need to leave home to arrive at the restaurant five minutes before Aunt Sally?

Here's one solution: First figure out how long it takes Aunt Sally to drive to the restaurant. She's driving 30 miles per hour, so for every hour she drives, she goes 30 miles. There are 60 minutes in an hour, so to find out the number of minutes it takes Aunt Sally to drive 5 miles:

Aunt Sally will arrive at the restaurant at 11:30 + 10 minutes = 11:40. You want to arrive five minutes before that at 11:35, so what time do you need to leave the house?

Perform the same calculations to determine how many minutes it takes you to drive 15 miles:

So you need to leave your house at 11:35 – 20 minutes = 11:15.