例如983－296，精确计算983－296=687，用整十或整百数估算980－300=680

741－459，精确计算741－459={#blank#}1{#/blank#}，用整十或整百数估算{#blank#}2{#/blank#}－{#blank#}3{#/blank#}={#blank#}4{#/blank#}

706－359={#blank#}1{#/blank#}

800－281={#blank#}2{#/blank#}

32-16=          13+29=          37+83=          78-28=

42-36=          123+47=         800+222=        543+106=

100-41=         450-190=         365-270=        733+67=

19+11=          5123-1123=       9000-800=       1000-16=

188+112=        560-320=         59+241=         555+444=