如果小红在小强东偏北40°的位置上,那么小强在小红的西偏南500位置上.… .(判断对错)
27+12=___________, 43-43+38=________;
24+15+30=________, 1+33+55=_________;
54+21-50=________.
先估一估,再比较大小.
32+40________70, 28+51_______80;
64+22________80, 41+47_______90.
口算.
65+13=________, 53+4=________;
68+10=________, 34+64=_______;
51+17=________.
口算.
11+41=_______, 24+45=_______;
32+46=_______, 47+52=_______;
34+62=_______, 13+46=_______.