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(一)两个“首同末合十”(十位数字相同,个位数字和为十)的两位数相乘。 法则:两个“首同末合十”的两位数相乘,先将首位数字乘以比它大1的数,所得的积乘以100,再加上两个因数中末位数字的积。 (二)两个“末同首台十”的两位数相乘
(a) Multiplying two “two digits with the same ten at the end and ten at the end” (the ten digits are the same and the ones digit is ten). Rule: Multiplies the two “first and last ten” by the two digits. First multiply the first digit by a number that is one greater than that, multiply the product by 100, and add the product of the last digit of the two factors. (II) Two-digit multiplication of the two “last same first station ten”