For this case we have the following multiplication:

We can rewrite this multiplication in the following way:

From here, we apply the distributive property.
We have then:

Therefore, Jack's strategy is:
Write the number in an expanded form and then apply the distributive property.
Answer:
Jack's strategy is:
Write the number in an expanded form and then apply the distributive property.
6.9
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Answer:
1. 650, 700 2. 840, 800 3. 370, 400 4. 80, 100 5. 620, 600 6. 250, 200 7. 970, 1,000 8. 330, 300 9. 450, 400 10. 210, 200 11. 100, 100 12. 710, 700
Step-by-step explanation: