
Grab
Years K  2 
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doug@blackdouglas.com.au
Summary
Estimating number is at the centre of this activity which is complemented by the Members activity Buttons. All the red plugs are placed in a bag and children try to withdraw a number of plugs which they first specify. The task is structured to support the development of subitising and mental arithmetic related to addition, subtraction, difference and complementary addition. Lots of variations and extensions are possible. Suitable for threading.


Materials
 One Poly Plug set per pair
 One calculator per child
 One bag, box or tub

Acknowledgement
This activity was designed by Wendy Batchelor, Ruth Court, Dione Parker, Julie Jacobs, Kingston Primary School.
Procedure
 Remove all the plugs from a red board and put them in the bag.
 The player thinks of the number of red plugs they want to withdraw from the bag and records it on their calculator.
 The player then reaches in and tries to grab that many in one handful. Now they:
 count the plugs
 compare with the target
 write or draw in their journal to explain the guess and the result
then replace the plugs and the other player tries.
 Repeat the process as often as interest allows with a view getting as close to the calculator guess as possible.
Extensions
 Children draw their own open number line (a line of any length with an arrow at each end) and record their guesses in one colour with marks above the line and in another colour with marks below the line.
 Use two or more boards and allow more than one dip into the bag with each hand, or one twohanded dip.
 When confidence has developed with red plugs, repeat the activity with the yellow/blue plugs. (What changes?)
 Students estimate the number they can grab with one hand, count the result and find the difference between the actual and the estimate. Record the difference (perhaps as a graph). Repeat the experiment and look for trends in the accuracy of estimates.


Content
 1:1 correspondence
 addition facts beyond 10
 addition facts to 10
 complementary addition
 counting
 data: collecting, recording, displaying
 estimating number
 number line  ordering, operations
 numeral recognition
 recording  calculator
 recording  written
 subitising
 visual and kinaesthetic representation of number
 writing numerals

Calculating Changes ... is a division of ... Mathematics Centre
