SSC JE Civil Engineering 2018 Set 4 Solved Paper

The staff reading taken on a staff held at a distance of 50 m from the instrument with the bubble central is 1.465 m. When the bubble is moved 4 divisions out of the centre, the staff reading is 1.472 m. What will be the radius of curvature (m) of the bubble tube, if the length of one division is 2 mm?