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1、 简便运算习题加法交换律(a+b=b+a)如:152+389+348=152+348+399=500+399=899习题:77+56+23 165+477+135 154+288+46加法结合律a+b+c=a+(b+c)如:591482118=591(482118)=591+600=1191习题:285+147+253 99+178+122 456+588+412 692+325+75加法交换律、结合律如:32296841 =32+68+29+41 加法交换律 =(32+68)+(29+41) 加法结合律 =100+70 =170习题:(148+64)+(52+136) 650+(171+35
2、0)+129 128+114+86+172乘法交换律ab=ba如:25454 =25445 =10045 =450025314 125278 406925乘法结合律:abc= a(bc)如:781258 12532 =78(1258) =125(84) =781000 =12584 =78000 =4000习题:52254 12572 12588 2532 2544 12548乘法交换律、结合律如:1254825 =1258425 乘法交换律=(1258)(425)乘法结合律=1000100=100000习题:1252532 乘法分配律:a(b+c)=ab+ac如:2757+2743 2799
3、+27 27 99 =27(57+43) =27(99+1) =27(100-1) =27100 =27100 =27100-271 =2700 =2700 =2673习题:6734+6766 12743-2743 27101-27 27 101 6721+6778+67 6723+6778+67-6712340+66120 2544 12588 85102 69102 789865+6599 587+87+874 减法运算性质; a-b-c=a-(b+c)=a-c-b如:781-178-122 721-488-121 745-(245+188) =781-(178+122) =721-121-488 =745-245-188 =781-300 =600-488 =500-188 =481 =112 =312习题: 456-273-127 623-169-223 553-(289+153 ) 772-456+228 689-(289-153 ) 136-88+164-112除法运算性质;a b c=a (bc)=a c b如:720 36 2 =720( 36 2) =720 72 =10习题:2700254 56002556 3900 (394)