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Part 1
There is more information than you need
Part 2
Part 3
How?
There are many ways, using factors. One method is shown below.
Part 1
378 = 6\times7\times9 cannot be written as the product of any other 3 numbers under 10
Only 6 is a factor of 60, only 7 is a factor of 21
60 = 6\times10 so the other two numbers are 2 and 5. 5 is only a factor of 40.
21 = 7\times3 so the other two numbers are 3 and 1. 3 is a only factor of 24.
Fill in what is missing to make 24 and 40. We never needed to use the number 288.
Part 2
210 = 7\times3\times10 = 7\times3\times2\times5 = 7\times6\times5 as the product of 3 numbers less than 10
5 is only a factor of 120 and 7 is only a factor of 126
126 = 7\times18. 6 already used so 126 = 7\times2\times9. 9 is only a factor of 72.
120 = 5\times24. 6 already used so 120 = 5\times3\times8. 9 is already in the 72 column, so 3 can't go in there too.
24 = 3\times2\times4 and 72 = 8\times9\times1
7 is only a factor of 28, 5 is only a factor of 40 and 90
144 = 8\times18 and 90 = 5\times18
Need to use the 8 for 40 or 48. Try the two options:
Part 3
135 = 5\times27 = 5\times3\times9 is the only product for 135
9 is not a factor of 12 or 60 and 5 is only a factor of 60
12 = 3\times1\times4 and 20 = 10\times2\times1 are the only ways to make 12 and 20, since the 5 is used
12 and 20 both need to use 1
60 = 2\times5\times6 and so the last number is 12