Write the measure -128 30' 45'' as a decimal to the nearest thousandth.

Answer 1

Raymond left a good answer, but the process I follow to do this would be:

Take the seconds and divide them by 60:

45/60 = 0.75

Add this number to the minutes:

30 + 0.75 = 30.75

Divide this number by 60:

30.75 / 60 = 0.5125

Add this number to the degrees :

128 + 0.5125 = 128.5125

Answer 2

30 minutes is half a degree

120, 30' = 120.5 degrees

45" is 45/60 = 3/4 of a minute.

a minute is 1/60 of a degree

3/4 of 1/60 = 1/80 of a degree

1/80 = 0.0125 degrees

120.5 + 0.0125 =

120.5125 degrees exactly

but if you want to round to nearest thousandth

you generally round .0125 to the nearest even number which means round down

to 120.512.

sometimes you round up, then it would be 120.513

it may depend on whether there's a cost involved in over or under estimating.