Question

帮忙解一道算数题好吗？

（9991×1999.1999+9991.9991×1999）÷2.0002

Answer 1

9991*1999+9991*0.1999+9991*1999+0.9991*19999=2×9991×1999+2×1999×0.9991=9991*1999*(2+0.0002)=9991*1999*2.0002
所以原式等于9991×1999即（10000—9）×（2000-1）=20000000-10000-18000+9=19972009.

Answer 2

（9991×1999.1999+9991.9991×1999）÷2.0002
=（9991×1999×1.0001+9991×1.0001×1999）÷2.0002
=9991×1999×2.0002÷2.0002
=9991×1999
=19972009