文档介绍：× 2= × 10= × 8= × 2= × 10= × = × 20= += += × 2= - = × = 6× = - = × = × 100= × = × = ÷ 7= × 100= ÷ = × 8= ÷ = ÷ 2= ÷ 28= ÷ = ÷ = × 9= ÷ 24= × = += - = ÷ 4= ÷ 13= ÷ 5= += 10÷ 20= 24÷ 15= × 10= × = × = × 1000= × = × = ÷ = ÷ 9= ÷ = ÷ 2= ÷ = ÷ = × 100= × 8= 0. 56÷ = × 4= × = ÷ = × = × = × = ÷ = 1÷ = × = ÷ = 0÷ = × 102= ÷ = 5× = - = ÷ ÷ = 5× = 24× = × = + = ÷ = 5÷ = ÷ = ÷ = ÷ 5= 7× = ÷ = - = ÷ = ÷ 8= × = 8+ = × 30= × = × = 0÷ 6= ÷ = ÷ = 2÷ 5= + 5= ÷ = ÷ = × = + = 8× = ÷ = 二、估算( 40 道) 1、 482 ÷ 62 628 ÷ 72 5580 ÷ 79 4185 ÷ 620 40÷ 2= 60× 6= 900 ÷ 9= 28+2= 14× 6= 700-300= 51-3= 21÷ 7= 21÷ 7= 18+16= 600 × 8= 78-28= 80+120= 5× 60= 15× 2= 12× 8= 36-12= 120-20= 16÷ 2= 50-25= 20+180= 200 × 4= 39÷ 3= 20-14= 16× 5= 40÷ 2= 21÷ 7= 40÷ 2= 40÷ 2= 40-25= 50+3= 660-600= 50+50= 600 × 8= 27+36= 20-20= 30+6= 5+17= 60÷