Question

Two pegs A and B are fixed on opposite bank of 50 m wide river. The level was set up at A and staff reading on peg A and B were observed as 1.350 and 1.55 m respectively. Thereafter the instrument was shifted and set at B. The staff reading on Pegs B and A were observed as 0.75 and 0.55m respectively. If R.L of Peg A is 100.2 m the RL of Peg B (in m)

• A. 100

Answer 1

The correct option is A 100
Let station B is below station A.

$\therefore \text{From Reciprocal leveling}{a}_1=1.350,b_1=1.550,a_2=0.55,b_2=0.750$

$\Delta h_{AB}=\frac{(b_1-a_1)+(b_2-a_2)}{2}$

$\Delta h_{AB}=\frac{(1.55-1.350)+(0.75-0.55)}{2}$

$\Delta h_{AB}=0.200$

R.L of B = R.L. of A - 0.200

$=100.2-0.200$

$=100.000m$