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Estimating
Objectives
To make reliable estimates of numbers up to 100.
Resources
Abacus Workbook 1 | 📄 Gift vouchers | A cloth | Two large mugs | Dried pasta shapes
Vocabulary
2-digit number | multiples | between
Today's Lesson
What to Get Ready
Prepare by printing out twelve sheets of the ‘gift vouchers’ from the 📄 Gift vouchers and cutting them up into individual vouchers. Place 20 of them on a tray, then place a cloth over the top.
Introduction
Tell your student that when you take away the cloth you want them to guess how many vouchers there are on the tray, but that they won’t have time to count them… they will need to estimate how many are there. Say, ‘An estimate is a sensible guess!’
Remove the cloth for two or three seconds, and then replace it. Ask your student for their estimate.
To support them here, you could prompt by saying, ‘About 10? About 20, 50 or 100?’
Discuss how if we guess an exact number like 57, it is unlikely to be correct, but our estimate might be accurate if we guess something like ‘about 50’.
Then count the vouchers together. How close was their estimate?
Next, show your student a pile of all of the vouchers (there should be 96). Ask them to estimate how many vouchers are in the pile. Is this harder to estimate? Why? Does having them close together in a pile help, or not?
Ask your student to count the vouchers.
Ask, ‘How might we keep track when counting such a large number?’
Suggest that we could put them in piles of 10 vouchers. Then we could count in tens to count the piles and add on any vouchers left over.
Main Activity
Give two large mugs of different pasta shapes (for example, twists and bows, and not more than 100 in each) to your student.
Your student should estimate which mug contains more pasta shapes, before estimating how many pieces are in each cup.
Your student should then count them, grouping them into tens to make the counting easier.
They should record both their estimate and their count.
Repeat with other pairs of mugs containing different numbers of pasta shapes or other small items, such as buttons, beads or small building bricks.
Extra Challenge
Play with your student – the aim is to get 5 points!
You take a large handful of pasta pieces and say how many you think you have.
For example, ‘I have 16 pasta pieces.’
Your student then counts the pieces. If you are within 1 either side of the correct number, you score a point.
Now swap over.
See if you can both get better at your estimating as you go along!
Workbook
To help your student consolidate their learning from today, please ask them to complete the activities on page 2 of Abacus Workbook 1.