In one minute, 1/9 of the pool is filled through the first pipe, and 1/10 through the second.

In one minute, 1/9 of the pool is filled through the first pipe, and 1/10 through the second. Which part of the pool will fill up through both pipes in 1/3 minute?

Initially, to calculate which part of the pool is filled with both pipes in one minute, for this, I added both fractions.
1/9 + 1/10, bring to a common denominator, which will be equal to 90. The first fraction is multiplied by 10, the second – by 9. We get the following expression:
10/90 + 9/90 = 19/90
That is, 19/90 of the pool is filled with two pipes in one minute.
Now multiply the resulting fraction by 1/3:
19/90 × 1/3 = 19/270.
Answer: Fill the 19/270 pool with two simultaneously operating pipes in one third of a minute.