Teaching and Group Activities for Understanding
Day 1 Teaching
Demonstrate using an empty number line to add 40 to 356. Use the same empty number line to model adding 41 and then 39. Show how the empty number line is useful when we add near multiples. Children use the same process to add 50 and 49 to 736. They then add 200, 199 and 201 to 358.
-- Make up word problems involving adding multiples and near multiples of 10 or 100 to a 3-digit number.
-- Add multiples and near multiples of 10 or 100 to a 3-digit number where the answer is more than 1000.
Day 2 Teaching
Ask children to show 385 – 50 on an empty number line on their whiteboards. What happens if we subtract 51, not 50? Children draw a hop back to 334, label it – 1, and label 334. How do we subtract 49 not 50? Draw a hop labelled + 1 to 336. Make sure that children are clear about which way to adjust. Repeat to subtract 200, 201 and 199 from 645.
Use the in-depth problem-solving investigation ‘Images of Addition and Subtraction’ from NCETM as today’s group activity.
Or, use these activities:
-- Use an empty number line to subtract near multiples of 10 and 100 from 3-digit numbers.