Sum with scientific notation. We just ignore the 10^5, because the two numbers have the same exponent and repeat it on the result of the normal sum between the numbers.
But, for example, if we had:
-> 5 x 10^4 + 5 x 10^5
We would need to equal the exponents to do the sum without having to multiply all those tens.
5 x 10^4 + 50 x 10^4
= 55 x 10^4
or 0.5 x 10^5 + 5 x 10^5
= 5.5 x 10^5
*They are the same results.
Now returning to the question:
-> 7.35 + 9.78 = 17.13
-> 17.13 x 10^5
You can prove it yourself:
-> 7.35 x 10^5 = 735,000
-> 9.78 x 10^5 = 978,000
-> 735,000 + 978,000 = 1,713,000
Or: 1713 x 10^3 or 17.13 x 10^5
Answer: The combined capacity of the two tower is 17.13 x 10^5 gallons of water.
