GATE 2021 AR – Question 57
A level at Q reads 3.5 m on a staff at P, whose RL is 96.5 m. Instrument height above Q is 1.25 m. Find RL of Q in metres, to two decimals.
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Show answer and explanation
Correct answer: 98.75 to 98.75
Explanation
The horizontal line of sight has RL 96.5+3.5=100.0 m. Q is 1.25 m below that line, so RL(Q)=100−1.25=98.75 m. Distinguish the instrument’s height above Q from the staff reading at P.