To find the height of Mt. Everest, we start with the height of Denali, which is about 20,000 feet. In scientific notation, this is \(2.0 \times 10^4\) feet.
We know that Mt. Everest is about \(9 \times 10^3\) feet higher than Denali.
Now, we can express the total height of Mt. Everest as follows:
\[ \text{Height of Mt. Everest} = \text{Height of Denali} + 9 \times 10^3 \]
Converting 20,000 feet into scientific notation gives us:
\[ \text{Height of Denali} = 2.0 \times 10^4 \]
The height of Mt. Everest then becomes:
\[ \text{Height of Mt. Everest} = 2.0 \times 10^4 + 9 \times 10^3 \]
To add these two numbers, we can convert \(9 \times 10^3\) into a form that is easier to combine with \(2.0 \times 10^4\):
\[ 9 \times 10^3 = 0.9 \times 10^4 \]
Now, the equation looks like this:
\[ \text{Height of Mt. Everest} = 2.0 \times 10^4 + 0.9 \times 10^4 = (2.0 + 0.9) \times 10^4 = 2.9 \times 10^4 \]
Thus, the height of Mt. Everest is approximately \(2.9 \times 10^4\) feet.
The correct answer is:
B. \(2.9 \times 10^4\) feet