To find the combined water capacity of the two water towers, we need to add their capacities:
- First water tower: \(7.35 \times 10^5\) gallons
- Second water tower: \(9.78 \times 10^5\) gallons
Now, we simply add these two numbers:
\[ 7.35 \times 10^5 + 9.78 \times 10^5 = (7.35 + 9.78) \times 10^5 = 17.13 \times 10^5 \]
Next, we need to express this in proper scientific notation. The number \(17.13\) can be rewritten as \(1.713 \times 10^1\). Combining this with the \(10^5\) from our original expression:
\[ 17.13 \times 10^5 = 1.713 \times 10^{1+5} = 1.713 \times 10^6 \]
So the combined water capacity of the two towers in scientific notation is:
1.713×10^6 gallons.