A rectangular channel is 4.0 m wide and carries a discharge of 2.0 m3/s with a depth of 0.4 m. The channel transitions to a maximum width contraction at a downstream location, without influencing the upstream flow conditions. The width (in meters) at the maximum contraction is ______________ (rounded off to 2 decimal places).
For a reconnaissance survey, it is necessary to obtain vertical aerial photographs of a terrain at an average scale of 1: 13000 using a camera. If the permissible flying height is assumed as 3000 m above a datum and the average terrain elevation is 1050 m above the datum, the required focal length (in mm) of the camera is
What is the CORRECT match between the survey instruments/parts of instruments shown in the table and the operations carried out with them?
| Instruments/Parts of instruments | Operations |
|---|---|
| P - Bubble tube | i - Tacheometry |
| Q - Plumb bob | ii - Minor movements |
| R - Tangent screw | iii - Centering |
| S - Stadia cross-wire | iv - Levelling |
To finalize the direction of a survey, four surveyors set up a theodolite at a station P and performed all the temporary adjustments. From the station P, each of the surveyors observed the bearing to a tower located at station Q with the same instrument without shifting it. The bearings observed by the surveyors are 30° 30' 00", 30° 29' 40", 30° 30' 20" and 30° 31' 20". Assuming that each measurement is taken with equal precision, the most probable value of the bearing is