一、两位数相乘细心观察,我们发现:两个十位数字相同,个位数字的和是10的两位数相乘,就等于用十位数字乘以比十位数字大1的数,再在所得的积后写上两个数的个位数字相乘的积.例如:83×87=72(8×9)21(3×7).原理:(10a+b)(10a+c)=100a2+10ab+10ac+bc.∵b+c=10,∴上式=100a2+10ab+1 First, double-digit multiplication by careful observation, we found that: the two tens digits are the same, the sum of the digits of the digits is the multiplication of the two digits of 10, it is equivalent to multiplying the tens digits by the digits greater than the tens digits by ones. , and then write the product of the multiplication of the digits of the two numbers after the resulting product. For example: 83×87=72(8×9)21(3×7). Principle: (10a+b)(10a+ c)=100a2+10ab+10ac+bc.∵b+c=10, ∴ above=100a2+10ab+1