估算.496×3≈ 346÷7≈ 21×49≈ 807÷9≈
新华书店新到一批书,这批书如果每包20本,要捆18包.如果要捆成15包,每包多少本?
口算:15110+21260=35110+22560=52410+21260=120000-115000=256000-156000=6523000-6421000=
估算:675500-510900≈703530-205120≈695540-578905≈503543-105780≈595500-478900≈735433-205540≈
估算:601530-205120≈687240-595905≈512500-145280≈586520-475450≈735433-205540≈595450-471246≈
估算:865500-578900≈803433-205000≈455464-205000≈866546-578900≈70123-105000≈553543-305540≈