Question

33X37 43X47 53X57怎样巧算?

Answer 1

1221,2021,3021
十位上数字与比它多1的数相乘的积加个位上数字直接相乘的积
如30x40+3x7=1221
40x50+3x7=2021
50x60+3x7=3021

Answer 2

33×37=3×（3+1）×100+3×7

追答

43×47=4×（4+1）×100+3×7

53×57=5×（5+1）×100+3×7

以此类推