8400 10060 6140 9200
5100 9120 8400 4800
16500 11500 22500 9500 9000
12600 27000 40200 53400 43200

解析：本题考查多位数乘两位数的估算方法。
答案为：
$49×104\approx 5000$，
$53×89\approx 4500$，
$78×38\approx 3200$，
$197×13\approx 2600$，
$88×31\approx 2700$，
$49×89\approx 4500$，
$519×17\approx 10000$，
$609×24\approx 14400$，
$709×6\approx 4200$，
$91×19\approx 1800$，
$208×11\approx 2000$，
$102×81\approx 8000$，
$29×49\approx 1500$，
$477×12\approx 4800$，
$799×19\approx 16000$，
$612×19\approx 12000$，
$108×17\approx 1800$，
$688×12\approx 7000$，
$703×21\approx 14000$，
$89×72\approx 6300$，
$489×21\approx 10000$。

$110×300=$
$290×0=$
$0×511=$
$150×0=$
$360×60=$
$470×90=$
$0×139=$
$220×50=$
$1300×6=$
$130×70=$
$140×9=$
$0×290=$
$1300×7=$
$130×80=$
$290×90=$
$0×176=$
$1200×8=$
$1500×0=$
$240×3=$
$240×30=$
$170×30=$

解析：这些题目都是基础的乘法口算题，主要考查乘法运算的掌握情况。特别是与0相乘的特殊性质，即任何数与0相乘都等于0。
答案：
$110×300 = 33000$
$290×0 = 0$
$0×511 = 0$
$150×0 = 0$
$360×60 = 21600$
$470×90 = 42300$
$0×139 = 0$
$220×50 = 11000$
$1300×6 = 7800$
$130×70 = 9100$
$140×9 = 1260$
$0×290 = 0$
$1300×7 = 9100$
$130×80 = 10400$
$290×90 = 26100$
$0×176 = 0$
$1200×8 = 9600$
$1500×0 = 0$
$240×3 = 720$
$240×30 = 7200$
$170×30 = 5100$