999X7+111X37
=(1000-1)x7+111x(40-3)
=(1000x7-1x7)+(111x40-111x3)
=(7000-7)+(4440-333)
=6993+4107
=11100
这道题运用到了乘法结合律。
999×7+111×37
=111×9×7+111×37
=111x63+111x37
=111×(63+37)
=111×100
=11100
999×7+111×37
=111×9×7+111×37
=111×(63+37)
=111×100
=11100
解:999x7+111x37
=111x9x7+111x37
=111x(63+37)
=111x100
=11100
999×7+111×37
=(1000-1)x7+111x(30+7)
=1000x7-1x7+111x30+111x7
=7000-7+3330+777
=7000+3000+(700+300+30+77-7)
=10000+1100
=11100