350的3倍是 ; 是210的5倍.
设a=,b=,则a+b= ,a﹣b= ,a×b= ,a÷b= .
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=_______.
在_______上填上“>”、“<”或“= ”. 35+23_______50, 27+32_______55; 43+34_______80, 53+26_______78; 23+72_______95, 16+41_______70; 35+44_______85, 52+46_______88.