To find out how many neon tetras can be housed in the aquarium, you can use the following formula:
\[ \text{Number of tetras} = \frac{\text{Total gallons of water}}{\text{Gallons needed per tetra}} \]
Given that the aquarium can hold \(1 \times 10^5\) gallons and each neon tetra needs 1.25 gallons of water, the calculation is:
\[ \text{Number of tetras} = \frac{1 \times 10^5 \text{ gallons}}{1.25 \text{ gallons/tetra}} \]
Now, performing the division:
\[ \text{Number of tetras} = \frac{1 \times 10^5}{1.25} \]
Converting 1.25 to a fraction:
\[ 1.25 = \frac{5}{4} \]
So this can also be written as:
\[ \text{Number of tetras} = 1 \times 10^5 \times \frac{4}{5} \]
Calculating:
\[ 1 \times 10^5 \times \frac{4}{5} = \frac{4 \times 10^5}{5} = \frac{4}{5} \times 10^5 \]
Calculating \(\frac{4}{5} = 0.8\):
\[ 0.8 \times 10^5 \]
To write \(0.8\) in scientific notation, it can be expressed as \(8 \times 10^{-1}\). Therefore, we get:
\[ 0.8 \times 10^5 = 8 \times 10^{-1} \times 10^5 = 8 \times 10^{4} \]
Thus, the number of neon tetras that the aquarium can house is:
\[ \boxed{8 \times 10^4} \]