The product of 11 and any 3-digit number also begins and ends with the ¿ rst and last digits of the multiplier, although the ¿ rst digit can change from carries. In the middle, insert the result of adding the ¿ rst and second digits and the second and third digits. Example: 314 × 11 ĺ 3 + 1 = 4 and 1 + 4 = 5; answer: 3454.
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- (no access) - Secrets of Mental Math (guidebook).pdf, p11
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