Well it all depends what measurement your answer has to be in.
Answer in cm- 12cm stays the same 143m becomes 14,300cm 398km becomes 39,800,000cm 778mm becomes 77.8cm Then you add them together 12+14,300+39,800,000+77.8=39,814,398.8 The answer stays the same cause it already has the right amount of sig figs so it's 39,814,398.8cm
Answer in m- 12cm becomes 0.12m 143m stays the same 398km becomes 398,000m 778mm becomes 0.778m Then you add them together 0.12+143+398,000+0.778=398,143.898 But then you have to round to the right amount of sig figs which would be to have two numbers after the decimal point so the answer would then be 398,143.90m
Answer in km- 12cm becomes 0.00012km 143m becomes 0.143km 398km stays the same 778mm becomes 0.000778 Then you add them together 0.00012+0.143+398+0.000778=398.143898km But then you have to round to the right amount of sig figs which would be to have three numbers after the decimal point so the answer would then be 398.144km
Answer in mm- 12cm becomes 120mm 143m becomes 143,000mm 398km becomes 398,000,000mm 778mm stays the same Then you add them together 120+143,000+398,000,000+778=398,143,898 The answer stays the same cause it already has the right amount of sig figs so it's 398,143,898mm
