Question 1056785
One pump can empty the pool in 36 hours. The second pump is twice faster. After both pumps, working together emptied  1/3  of a pool the second pump broke. The first pump finished the job. How long did it take to empty the pool?
<pre>Both pumps worked for 4 hours, and emptied {{{1/3}}} of pool.
The 1st (slower) pump took 24 hours to empty remaining {{{2/3}}} of pool. 
Total time taken to empty pool: {{{highlight_green(matrix(1,4, 4 + 24, or, 28, hours))}}}