To find the depth of Lake Segundo, we need to multiply the depth of Lake Profondo by the fraction that represents Lake Segundo's depth relative to Lake Profondo.
Here's the calculation:
- Lake Profondo's depth: 84 feet
- Lake Segundo is \( \frac{5}{6} \) as deep as Lake Profondo.
To find the depth of Lake Segundo, we multiply:
\[ \text{Depth of Lake Segundo} = \text{Depth of Lake Profondo} \times \frac{5}{6} = 84 \times \frac{5}{6} \]
Calculating this step by step:
\[ = \frac{84 \times 5}{6} \]
First, calculate \( 84 \times 5 \):
\[ 84 \times 5 = 420 \]
Now divide by 6:
\[ \frac{420}{6} = 70 \]
Therefore, the depth of Lake Segundo is 70 feet. Since this depth is below sea level, we express it as a negative number for elevation:
\[ \text{Elevation at the bottom of Lake Segundo} = -70 , \text{ft} \]
Thus, the answer is indeed:
-70 ft.