An 18 in long rebar is driven into the ground until it touches an underground pipe. A backsight to a benchmark with an elevation of 393.66 ft is taken with an automatic level. The backsight has a rod reading of 7.56 ft. A foresight is taken to the rod resting on top of the rebar. The rod reading is 1.01 ft. What is the elevation of the top of the pipe

398.71 ft

Step-by-step explanation:

Length of rebar = 18 inches  = 1.5 ft

Elevation  = 393.66 ft

Reading of backsight on Benchmark= 7.56 ft

Rod reading = 1.10 ft

First step : determine height of Instrument been used

= elevation + backsight on Benchmark

= 393.66 + 7.56 = 401.22 ft

Elevation of top of rebar

= 401.22  - 1.01  = 400.21 ft

Finally determine the elevation of the top of the pipe

= 400.21 - length of Bar

= 400.21 - 1.5 = 398.71 ft

d is correct

step-by-step explanation:

both equations and proportions are better.