Answer:
3.6 hours
Step-by-step explanation:
step 1
we know that
Pipe A fills a tank in 9 hours
so
The 100% of the tank is filled in 9 hours
using proportion
Find out what percentage of the tank is filled in 1 hour
[tex]\frac{100\%}{9}=\frac{x\%}{1} \\\\ x=11.11\%[/tex]
step 2
we know that
Pipe B fills a tank in 6 hours
so
The 100% of the tank is filled in 6 hours
using proportion
Find out what percentage of the tank is filled in 1 hour
[tex]\frac{100\%}{6}=\frac{x\%}{1} \\\\ x=16.67\%[/tex]
step 3
we know that
In one hour the percentage of the tank fill with both pipes is equal to
[tex]11.11\%+16.67\%=27.78\%[/tex]
using proportion
Find out how long it takes to fill the tank 100%.
[tex]\frac{1}{27.78\%}=\frac{x}{100\%}\\\\ x=100/27.78\\ \\x=3.6\ hours[/tex]
