An elevator descends into a mine shaft at the rate of `6` m/min. If the descent starts from `20` m above the ground level, how long will it take to reach `370` m ?

Options

A. 4 hr. 5 min
B. 3 hr. 5 min
C. 1 hr. 5 min
D. 2 hr. 5 min

Answer

To solve the problem step by step, we need to determine how long it will take for the elevator to descend from 20 meters above ground level to 370 meters below ground level.

### Step 1: Determine the total distance to be traveled
The elevator starts at 20 meters above ground level and descends to 370 meters below ground level.

- The total distance from 20 meters above ground to ground level is 20 meters.
- The distance from ground level to 370 meters below ground is 370 meters.

Thus, the total distance to be traveled is:
\[ \text{Total Distance} = 20 \text{ m} + 370 \text{ m} = 390 \text{ m} \]

### Step 2: Use the formula for speed, distance, and time
We know that:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]
We can rearrange this formula to find time:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]

### Step 3: Substitute the known values into the formula
We have:
- Distance = 390 m
- Speed = 6 m/min

Substituting these values into the formula gives:
\[ \text{Time} = \frac{390 \text{ m}}{6 \text{ m/min}} = 65 \text{ minutes} \]

### Step 4: Convert time into hours and minutes
Since there are 60 minutes in an hour, we can convert 65 minutes into hours and minutes:
- 60 minutes = 1 hour
- Remaining minutes = 65 - 60 = 5 minutes

Thus, the total time taken is:
\[ \text{Time} = 1 \text{ hour} \text{ and } 5 \text{ minutes} \]

### Final Answer
The elevator will take **1 hour and 5 minutes** to reach 370 meters below ground level.

---