Dear Parents and Caregivers, We appreciate the support you give to your child in learning mathematics. We would like to share some information to help you better understand Arizona’s College and Career Ready Standards. This is one of a series of letters intended to help you understand the work your child is bringing home. We will highlight new language and strategies we will use to build understanding, help students make sense of numbers and know common methods we learned in school. This letter is about solving problems with addition and subtraction involving measurement in third grade. End-­‐of-­‐year goal In second grade, students began to demonstrate fluency with addition and subtraction and applied various addition and subtraction strategies up to 1000. They also explored standard units of measure. Now students will develop conceptual understanding of measuring intervals of time, liquid volume, weight/mass, perimeter, and use measurement as a context for further development of fluency in addition and subtraction. Solve addition and subtraction problems Elapsed Time Students will solve word problems involving addition and subtraction of time intervals. They may represent this on a number line. The bell rang at 12:22 for children to go out to recess. It rang again at 12:47. How many minutes was recess? To show the elapsed time (time that has passed) students could draw a number line showing the minutes, starting at 12:22. Then they would count up to the nearest 5 minutes (25) and continue counting by 5s to 45 minutes. Then count the last 2 minutes to 12:47. To find the total elapsed time, add 3 + 20 + 2 = 25 minutes. 3 + (5 + 5 + 5 + 5) + 2 22 25 30 35 40 45 47 Mesa Public Schools/Grade 3/Add&SubMeasure/2013 Authorization to reprint or disseminate must be granted by Mesa Public Schools (February-­‐2014). Liquid Volume When solving problems involving adding and subtracting liquid volume, students will use liters and milliliters. They will have multiple opportunities in the classroom to fill containers to learn about liquid volume. Students may solve problems like this: •
In your science experiment, you poured 20 milliliters of water into one beaker and 20 milliliters into another beaker. You placed one beaker on the counter and one outside in the sun for two days. Then you measured the amount of water in each beaker. Using your measurements, find how much water evaporated from each beaker. If there is a difference in the amounts left in each beaker, explain why you think this is so. Students will use subtraction to find the amount that is left in each beaker. They may also use subtraction when comparing the difference in the amount of water in the beakers, to see how much more one beaker may have than the other. Weight Students might also measure the weight of several sports balls, such as a kickball, a baseball, and a beach ball, using grams. To compare the weights and determine how much greater or less one ball weighed than another, they would use subtraction. They may discover that the largest ball may not be the heaviest. Perimeter Measuring the perimeter of rectangles and other polygons is one application for addition and subtraction skills. Students may be solving real-­‐world problems such as finding the total perimeter of a basketball court, determining the missing length of a side of a fence that surrounds the perimeter of the playground, or measuring the perimeter of two classrooms and finding how much smaller one is than the other. Students may draw a picture to illustrate the lengths and to help them determine an operation (addition or subtraction) to use. How to help at home •
Allow your child to experiment with liquid volume using a metric measuring cup. Pose addition and subtraction problems about the measurements. •
Ask your child to write the starting and stopping time for a trip in the car or a TV show. Ask him/her to determine the elapsed time of the trip or show. •
Watch these videos on elapsed time from LearnZillion: http://learnzillion.com/lessonsets/173-­‐solve-­‐elapsed-­‐time-­‐word-­‐problems •
Remember, making mistakes is a part of learning. Mesa Public Schools/Grade 3/Add&SubMeasure/2013 Authorization to reprint or disseminate must be granted by Mesa Public Schools (February-­‐2014).