几道提高的数学题
问题描述：
几道提高的数学题
用地等式来简算,全过程只能用口算
172X56一79X36一93X3
54十99X99十45
9999X2222十3333X3334
答
172X56-79X36-93X3
=172X(36+20)-79X36-93X3
=(172-79)X36+172X20-93X3
=93X36+172X20-93X3
=93X33+172X20
=3069+3440
=5509谢谢，还有几道题呢第二题54+99X99+45=54+45+99X99=99+99X99=99X(99+1)=99x100=9900都是有简便方法的第三题呢第三题=9999X2222+3333X3333+3333=3333X6666+3333X3333+3333=3333X9999+3333=3333X10000=33330000