math/chemistry
posted by kayla on .
I don't understand how to round to significant digits
565 lb * 30 ft
4900 ft/ 144 sec
786 hr * 23 miles per hour

The first one will be to one significant digit because of the 30 has only one sig digit.
The second will have two because of the numerator.
The third will have 2 because of the denominator. 
I under stand this but once i get the answers i really don't know how to do it these re the answers i get
1. 16950
2. 34.02777778
3. 18078
but i don't understand how to round it like would the first one be 10?