Pre-Lesson Preparation

Open the Marty the Robot app and build the code, from the teacher guide, into the workspace:

This code will have Marty move a set distance. The idea is that Marty will be used initially to inform estimates: learners think an object has a length of about 15 cm or about 6 inches. Marty can be coded to walk that distance. Learners will look at the length of the object and compare this to the distance Marty walked to reinforce the estimate or to encourage learners to re-estimate.

Warm-Up

Have a collection of bean bags and a target on the ground. Learners should stand about 13 ft (4 metres) from the target. Learners are attempting to hit the target with their toss.

Below is the procedure for the activity

Have a straight line of tape from the target out the way toward where learners are standing. Mark the tape every 4 inches (about every 10 cm). Do this for 3 lines of tape starting from the target. Put learners in partners or small groups.

1. Inform learners that they are trying to get the beanbag as close to the target as they can. After they through, they need to estimate about how far away they were from the target. Have learners record the estimate on a scoring page (in the resources section but feel free to use scrap paper instead.)

2. Following the estimates, learners will go to their bean bag and measure how far away their throw was from the target using a ruler.

3. Have them record the actual measurement and decide if their estimate was close. Reinforce that close does not mean the same as.

4. Allow every learner in a partnership or group to have a throw, an estimate and an opportunity to measure.

5. Repeat as desired.

The goal is to have learners practice estimating first and measuring second. Additionally, it is to judge estimates as good or much to high or low. A good estimate is not the same as an exact measurement, which needs to be reinforced.

Get Learning

Prepare an area for whole-class learning where there are a range of straight sided objects with space around each. Have a piece of scrap paper, a post it note, or the page from the resources section beside each one. Have a ruler available so that you can show learners exact measurements in the device and then have them think about how long the objects are: the ruler is for the purpose of estimation at this point. Have learners compare the length of the line to what they think is a good measurement on the ruler.

For the first example, have the ruler reasonably close to the ruler. for subsequent objects, do not move the ruler but refer to objects that are farther and farther away from the ruler. Ask learners to look at the first object on display and give an estimate of about how long they think it is. If wanted, allow learners to hold the object but do not let them hold the ruler alongside. Come to a class consensus, recording perhaps two or three estimates and write them on the paper beside the object.

Using the code with Marty, enter the number of steps that learners gave as their estimate, choosing the option for inches or cm. Run the code by setting up Marty against the beginning of the object. Press thegreen flag to have Marty walk the estimated length. Feel free to do this more than once if the estimates were signficantly diverse. Record the steps Marty took as too many or too few, or some other description.

Take the ruler and model measuring the object by placing them side by side, lining up the 0 mark against the beginning of the object. An alternative would be to purposefully misplace the ruler and have learners correct your work. Record the actual measurement on the page and take time to compare:

• the estimates we gave were all not enough / too much
• the estimates we gave were very close

Ensure that there is praise given for taking a chance in sharing their ideas and that with estimates we get better each time we do them. Repeat the process with other objects, keeping the ruler where it was initially placed. Now learners have the ruler and the objects with the exact measurements, this process of building a bank of lengths will slowly increase their ability to see about how long something is.

Below are ideas for preparing progressively more challenging lengths. You will notice that initially, the objects are 3d, they then move to drawn shapes and finally as line segments. This process of concrete to abstract will support learners in their estimation journey.

images for display

video of Marty walking after estimation

Time for Practice

Share with learners the activity page that they will work on, either in small groups or individually. There are two varieties, one has metric and one is customary measurements.

Below are ideas as to how to make best use of the activity page.

• The activity pages have a ruler that is to scale for an A4 or letter page.
• The ruler is there as a comparison to support estimation but also to dissuade learners from immediately measuring and then calling that measurement their estimation.
• Learners will also need a ruler to carry out the actual measurement but stress that estimation come before the measurement.
• After each shape, and then line, has a recorded estimation, have learners use the ruler to determine the actual measurement.
• Learners will improve in their estimates as they progress through the activity because of the continual reinforcement of the estimate - measure - compare cycle.

The goal is for learners' estimates to get closer and closer to the actual measurement as the activity progresses.

Cool Down

Bring learners back together to discuss where they were successful with counting and adding.

Suggested questions you might ask:

• I think estimates are hard to do, did anyone else think estimates were hard at the start?
• Who got better at their estimates?
• Who thinks they could estimate even longer objects?

If you use a formative assessment strategy, like thumbs up or thumbs down, use that here to get a feel for learner confidence with the topic.

Carry out any end of lesson routines.