利用商不变的规律口算下面各题。3600÷600= 4800÷300= 7200÷900= 3200÷400=5800÷200= 2500÷50= 960÷80= 8100÷300=4700÷100= 1600÷160= 1200÷50= 63000÷700=
4+2= 7-4= 7-6 =10-8= 10-3= 5+3=
6+3= 7+2= 9+1=7+1= 8-5= 6-3=
8-4= 6+0= 5+2=10-9= 10-8= 8+2=
9-4= 10-3= 9-3=10-7= 7-5= 6-4=
8-5= 8+2= 9-7=4+4= 10-5= 4+2=