N3A4TNp19
Answer to Problem 19:
7 ´ 10 = 70
To use halving and doubling, I would take half of the first factor, which is 14, and make it a 7. I would double the second factor, which is 5, and make it a 10. Then I would multiply 7 ´ 10 to get 70.
TEACHER NOTES:
To use halving and doubling, take half of the first factor and multiply it by double the second factor (e.g., change 14 ´ 5 to 7 ´ 10).
Note: Additional mental math strategies and activities may be found in Number Sense: Simple Effective Number Sense Experiences.[1]
[1] McIntosh, A., Reys, B., Reys, R., & Hope, J. (1997). Number sense: Simple effective number sense experiences. Palo Alto, CA: Dale Seymour Publications.