The expression in terms of "n" for how much of the fire they will extinguish in 1 minute when both hoses are turned on together is [tex]\frac{n + 14}{7n + 49}[/tex]
Solution:
Given that,
Hose A, when turned on alone, can extinguish the fire in 7 minutes
Hose B takes "n" minutes more time than hose A
Hose takes (n + 7) minutes to extinguish the fire
STEP 1: Calculate how much work (here work is to extinguish the fire) each person does in one minute
[tex]Hose A = \frac{1}{7}th \text{ of the work }\\\\Hose B = \frac{1}{n+7}th \text{ of the work }[/tex]
STEP 2: Add up the amount of work done by each person in one minute
Work done in one minute when both are working together:
[tex]\rightarrow \frac{1}{7} + \frac{1}{n + 7}\\\\\rightarrow \frac{n + 7 + 7}{7n + 49}\\\\\rightarrow \frac{n + 14}{7n + 49}[/tex]
Therefore, the expression in terms of "n" for how much of the fire they will extinguish in 1 minute when both hoses are turned on together is:
[tex]\frac{n + 14}{7n + 49}[/tex]
