Controller of Mines • 2026 • Technical Paper-III
Explain the difference between Net Present Value (NPV) and Internal Rate of Return (IRR).
Controller of Mines • 2026 • Technical Paper-III
Primary crushers are mainly classified into:
A)
Jaw and Cone crusher
B)
Jaw and Gyratory crusher
C)
Roll and Hammer crusher
D)
Cone and Roll crusher
Primary crushers are used for the first stage of size reduction, handling the largest feed sizes. The two main types of primary crushers are jaw crushers and gyratory crushers. Cone crushers, roll crushers, and hammer crushers are generally used in secondary or tertiary crushing, not primarily as primary crushers.
Controller of Mines • 2026 • Technical Paper-III
If the “Coefficient of Variation” of ore grade in two different blocks is 15% and 30% respectively, which block has higher relative variability?
A)
The block with 15%
B)
The block with 30%
C)
Both have equal variability
D)
Coefficient of variation does not measure variability
The coefficient of variation (CV) measures relative variability. A higher CV means greater dispersion relative to the mean. Since 30% is greater than 15%, the block with 30% coefficient of variation has higher relative variability. Option (a) is lower, option (c) is false because the values are different, and option (d) is incorrect because CV is specifically used to measure relative variability.
Controller of Mines • 2026 • Technical Paper-III
In the sequence of numbers 5, 8, 13, x, 34, 55, 89. The value of x is:
A)
20
B)
21
C)
23
D)
29
This is a Fibonacci-type sequence, where each term is the sum of the previous two terms: 5, 8, 13 (=5+8), 21 (=8+13), 34 (=13+21), 55 (=21+34), 89 (=34+55). Therefore, x = 21. The other options do not satisfy the pattern.
Controller of Mines • 2026 • Technical Paper-III
An “Exponential Distribution” is frequently used in mine reliability engineering to represent:
A)
Time between equipment failures.
B)
The shape of a blast fragment.
C)
The depth of a borehole.
D)
The market price of minerals.
The exponential distribution is commonly used in reliability engineering to model the waiting time between successive random events, especially failures. In mining, it is often applied to represent time between equipment failures or breakdowns. The other options are unrelated to this distribution: blast fragment shape, borehole depth, and market price of minerals are not standard uses of the exponential model.
Controller of Mines • 2026 • Technical Paper-III
Coefficient of variation is a measure of:
A)
Central tendency
B)
Absolute dispersion
C)
Relative dispersion
D)
Skewness
The coefficient of variation (CV) is defined as standard deviation divided by mean, usually expressed as a percentage. Since it compares variability relative to the average, it is a measure of relative dispersion. It is not a measure of central tendency, absolute dispersion, or skewness.
Controller of Mines • 2026 • Technical Paper-III
Karl Pearson’s coefficient of skewness is zero when:
A)
Mean Mode
B)
Mean = Mode
C)
Mean > Mode
D)
Mode > Mean
Karl Pearson’s coefficient of skewness is given by (Mean − Mode) / Standard Deviation. It becomes zero only when the numerator is zero, i.e., Mean = Mode. Therefore, the distribution is perfectly symmetrical. The other options would give a non-zero skewness.
Controller of Mines • 2026 • Technical Paper-III
Discuss the role of Indian Bureau of Mines under MCDR, 2017.
Controller of Mines • 2026 • Technical Paper-III
The coefficient of variation is given by:
A)
M / 100
B)
/ M 100
C)
/ N 100
D)
M.N 100
The coefficient of variation (CV) is defined as the ratio of standard deviation to mean, expressed as a percentage: CV = (σ / M) × 100, where σ is the standard deviation and M is the mean. Option (a) is the reciprocal of the correct formula, while (c) and (d) are not standard definitions of coefficient of variation.
Controller of Mines • 2026 • Technical Paper-III
What is the meaning of the idiom “To tilt at windmills”?
A)
To attack imaginary enemies or grievances.
B)
To engage in agriculture.
C)
To build renewable energy sources.
D)
To behave in a strange manner.
The idiom “to tilt at windmills” comes from Don Quixote, where the character mistakes windmills for giants and attacks them. It means to fight against imaginary enemies, or to pursue futile battles against something that is not really a threat. Option (a) matches this meaning. Option (b) is unrelated to the idiom, (c) is about energy generation and has no connection, and (d) is too general and does not capture the specific idiomatic sense.
Controller of Mines • 2026 • Technical Paper-III
If the radius of sphere is decreased by 24%, by what per cent does the surface area decrease?
A)
44%
B)
49%
C)
42.24%
D)
46.2%
Surface area of a sphere is proportional to r². If the radius is decreased by 24%, the new radius becomes 76% of the original. So the new surface area becomes (0.76)² = 0.5776 of the original. Therefore, the decrease in surface area = 1 - 0.5776 = 0.4224 = 42.24%. Hence, the correct option is (c).
Controller of Mines • 2026 • Technical Paper-III
Explain the role and primary functions of the Directorate General of Mines Safety (DGMS) in regulating safety in Indian mines.
Controller of Mines • 2026 • Technical Paper-III
Briefly outline the basic safety precautions that must be strictly followed during the storage and transport of explosives in a mine, referencing the Explosives Rules, 2008.
Controller of Mines • 2026 • Technical Paper-III
In the context of minor mineral concessions in Mizoram, define “Royalty” and “Dead Rent”. What is the standard rule regarding the payment of these two charges by a leaseholder?
Controller of Mines • 2026 • Technical Paper-III
Jigging is a process of separating particles based on their density using:
A)
A constant horizontal flow of air.
B)
A vertical pulsating column of water.
C)
High-tension electrical wires.
D)
Chemical reagents.
Jigging is a gravity separation process used in mineral processing. It separates particles mainly on the basis of density by using repeated upward and downward pulsations of water through a bed of particles. The denser particles settle faster, while lighter particles are carried upward. Hence, the correct choice is a vertical pulsating column of water. Option (a) describes air-based pneumatic separation, (c) is related to electrostatic separation, and (d) refers to froth flotation or chemical separation methods.
Controller of Mines • 2026 • Technical Paper-III
Under National Mineral Policy, 2019, the State acts as:
A)
Absolute owner of mineral resource
B)
Regulatory authority without fiduciary role
C)
Trustee of mineral resources on behalf of the people
D)
Revenue collecting agency only
The National Mineral Policy, 2019 states that the State is not the absolute owner of mineral resources in a proprietary sense; rather, it holds mineral resources in trust for the benefit of the people and future generations. This reflects the public trust doctrine. Therefore, option (c) is correct. Options (a), (b), and (d) are incorrect because they either overstate ownership, deny the fiduciary role, or reduce the State’s role only to revenue collection.
Controller of Mines • 2026 • Technical Paper-III
Explain the general safety provisions under Coal Mines Regulations, 2017.
Controller of Mines • 2026 • Technical Paper-III
Choose the word most nearly opposite in meaning to ABSTEMIOUS:
A)
Self-indulgent
B)
Frugal
C)
Temperate
D)
Moderate
ABSTEMIOUS means restrained, sparing, or self-denying, especially in eating and drinking. The word most nearly opposite is Self-indulgent, which means indulging one's desires excessively. Frugal, temperate, and moderate are all close in meaning to abstemious, not opposites.
Controller of Mines • 2026 • Technical Paper-III
For doing a certain job, a boy is offered Rs. 5 on the first day. Rs. 15 on the second day, Rs. 45 on the third day and so on. How much will the boy earn at the end of seven days?
A)
Rs. 5486
B)
Rs. 5484
C)
Rs. 5465
D)
Rs. 5450
The payments form a geometric progression: 5, 15, 45, ... with first term a = 5 and common ratio r = 3.
Sum for 7 days:
S7 = a(r^7 - 1)/(r - 1)
= 5(3^7 - 1)/(3 - 1)
= 5(2187 - 1)/2
= 5 × 2186 / 2
= 5 × 1093
= 5465.
Wait—this value matches option (c), not (b). So the correct total is Rs. 5465. The question’s listed options include Rs. 5465, which is the correct answer; the other options are incorrect.
Therefore, the correct option is (c).
Controller of Mines • 2026 • Technical Paper-III
If you are facing North-West and turn 225 degrees clockwise, which direction are you facing?
A)
East
B)
South-West
C)
North
D)
South
North-West is halfway between North and West. Turning 225° clockwise means moving 180° + 45°, i.e., 4.5 direction steps of 45° each. From North-West, clockwise: North-West → North → North-East → East → South-East → South. Equivalently, 225° clockwise from North-West lands on South-West. So the correct direction is South-West.
Controller of Mines • 2026 • Technical Paper-II
What indication do we get when contour lines lie closer?
A)
It means that slope of land is gentle
B)
It means that slope of land is steep
C)
It means that the land is flat
D)
It does not give any indication
Contour lines represent points of equal elevation. When the lines are closer together, the elevation changes rapidly over a short horizontal distance, which indicates a steep slope. If the contour lines are farther apart, the slope is gentle. Therefore, option (b) is correct.
Controller of Mines • 2026 • Technical Paper-II
Explain the factors affecting the selection of a mine pump and define the terms capacity and head.
Controller of Mines • 2026 • Technical Paper-II
In ambient air of industrial area, the permissible concentration of suspended particulate matter (PM10) measured on 24 hours average in µg/m3 is:
A)
100
B)
200
C)
300
D)
400
As per the National Ambient Air Quality Standards (NAAQS) in India, the permissible 24-hour average concentration of PM10 in industrial/residential/rural and other areas is 100 µg/m3. Therefore, the correct answer is 100. The other options are higher than the prescribed standard.
Controller of Mines • 2026 • Technical Paper-II
A coal heading 4m wide and 2.5 metre high has an advance of 1 metre per cycle. The amount of explosive used in blasting is 6 kg. Taking specific gravity of coal as 1.5, calculate the powder factor.
Controller of Mines • 2026 • Technical Paper-II
Briefly discuss the main ingredients of an explosive, namely: the Oxidizer, Fuel, and Sensitizer.
