If the value of ore is Rs. 600 per tonne, production cost Rs. 400 per tonne, and cost of overburden removal Rs. 50 per m³, the break-even stripping ratio in m³/tonne is

When the occurrence of mineral (e.g. rare minerals) is randomly distributed in a rock then which of the distribution pattern is statistically followed?

A. Normal distribution

B. Skewed distribution

C. Lognormal distribution

D. Poisson distribution

Which of the following combination of SDL based mining is expected to give best production and productivity of SDL?

A. 3 level heading district

B. 4 level heading district

C. 5 level heading district

D. 6 level heading district

It is very difficult to control shaley roof if coal is not left with the shale why?

A. It is weak in nature

B. It has weathering effect

C. It has great affinity to absorb moisture and get departed from immediate roof

D. It reacts with coaly surface

In connection with lowering or raising of persons by means of bucket etc. for a shaft exceeding "A" m in depth, there shall be significant cover overhead for protection from things falling down the shaft. A is given by

A. 130m

B. 190m

C. 270m

D. 500m