839 is estimated to be 840÷6= 140, so it is estimated to be 140 and accurate to 839÷6= 1395.

The estimate of 478 is 480÷8=60, so the accurate estimate is 60. 478÷8=596.

The estimate of 637 is 630÷9=70, so the accurate estimate is 70.

287 is estimated to be 280, 43 is estimated to be 40,280 ÷ 40 = 7, so the accurate estimate is 7. 287÷43=6? 29

590 is estimated to be 600, 27 is estimated to be 30,600 ÷ 30 = 20, so the accurate estimate is 20. 590÷27=2 1? 23

432 is estimated to be 450, 48 is estimated to be 50,450 ÷ 50 = 9, so the accurate estimate is 9.