According to recommendations of IS: 4987–1968, how many raingauges would be required for 1170 square kilometer hilly area?
- A6
- B7
- C9Correct
- DNone of above
Solution
Concept
Raingauge density (IS 4987)
Formula
Hilly area: 1 gauge per about 130 km²
Step-by-step solution
1. IS 4987 recommends 1 gauge per 520 km² in plains, 260–390 km² in elevated regions and 130 km² in hilly areas. 2. N = 1170/130 = 9.
Explanation
Hilly areas need denser gauges.
Why the other options are wrong
6 and 7 correspond to a coarser density.
Shortcut
1170/130 = 9.
Correct answer: C) 9