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What are some of the easier ways to get at the following mentally:

a) 129 * 113

b) 131 * 143

c) 539 * 15 ( easier than add half of 5390 to 5390)

All of the above are from past TMSCA Elementary Number Sense Tests for Grades 4 & 5.

Thanks much,
Phil

For c, I'd do 540 * 15 - 15 and do the normal 15 trick with 540.

Thanks much for the help!

To answer 111*452, would Triple LOIF be the best method or are there better alternatives?

Thanks,
Phil

You can also extend that to multiplying by 1111 and 11111.