99.99乘77.77+33.33乘66.66怎么简便计算

99.99×77.77+33.33×66.66
=99.99×77.77+33.33×（3×22.22）
=99.99×77.77+（33.33×3）×22.22
=99.99×77.77+99.99×22.22
=99.99×（77.77+22.22）
=99.99×99.99
=9998.0001