Determine the elevation of B.M. 2 from the following notes. Check arithmetic by adding F.S.s and B.S.s. Sta. B.S. H.I. F.S. Elevation B.M. 1 1.21 50.00 T.P. 1 6.20 4.65 T.P. 2 4.82 3.11 T.P. 3 3.03 5.22 B.M. 2 3.16

 Problem 

Determine the elevation of B.M. 2 from the following notes. Check arithmetic by adding F.S.s and B.S.s.

Sta.	B.S.	H.I.	F.S.	Elevation
B.M. 1	1.21			50.00
T.P. 1	6.20		4.65
T.P. 2	4.82		3.11
T.P. 3	3.03		5.22
B.M. 2			3.16

Solution  

Sta.	B.S.	H.I.	F.S.	Elevation
B.M. 1	1.21			50.00
		51.21
T.P.1	6.20		4.65	46.56
		52.76
T.P. 2	4.82		3.11	49.65
		54.47
T.P. 3	3.03		5.22	49.65
		52.28
B.M. 2			3.16	49.12
Sum	15.26		16.14

OR

Sta.	B.S.	H.I.	F.S.	Elevation
B.M. 1	1.21	51.21		50.00
T.P.1	6.20	52.76	4.65	46.56
T.P. 2	4.82	54.47	3.11	49.65
T.P. 3	3.03	52.28	5.22	49.65
B.M. 2			3.16	49.12
Sum	15.26		16.14

Sum (B.S.) - Sum (F.S.) = 15.26 - 16.14 = -0.88

Elev B.M. 2 - Elev B.M. 1 = 49.12 - 50.00 = -0.88

Arithmetic check: do these differences equal?

Sum (B.S.) - Sum (F.S.) = Elev B.M. 2 - Elev B.M. 1

Answer: yes, they do equal