例如468＋439，精确计算468＋439=907，用整十或整百数估算470＋440=910

856＋95，精确计算856＋95={#blank#}1{#/blank#}，用整十或整百数估算{#blank#}2{#/blank#}+{#blank#}3{#/blank#}={#blank#}4{#/blank#}

①165+356

②286-177

③359+262

④302-167

⑤※230-218

⑥※271+99

①506+399＝

②700﹣279＝

③170+850＝

④*902﹣356＝

⑤340﹣170＝

⑥508+296＝

⑦904﹣287＝

⑧*234+408＝

422-278        148+225        800-341        1000-325          354+646        

{#blank#}1{#/blank#}>{#blank#}2{#/blank#}>{#blank#}3{#/blank#}>{#blank#}4{#/blank#}>{#blank#}5{#/blank#}