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Class 23CG (Year 2 and 3) at Old Orchard Primary School in Melbourne Australia, think the missing dominoes are 6-6, 6-5, 5-5 and 6-4.
We first worked out that there should be 28 dominoes in total. See attached work.
We worked out there were 8 of each number on the dominoes.
We multiplied the 8 by 21 (the total of all numbers on the dominoes) to get an expected total of 168 dots.
We next subtracted 125 from 168 and knew that we had 43 dots missing and 4 dominoes missing.
We then took away 12 (6-6) from 43 to get 31. We then took away 11 (5-6) to leave 20.
We then knew we had to take away 2 10s, the only way we could do this was 5-5 and 6-4.