Answer:
it will take them 1.71 hours to finish cutting the lawn if they work together.
Step-by-step explanation:
If Marsha cuts the lawn by herself it will take her 3 hours, this mean that in one hour she cuts 1/3 of the lawn.
On the other hand Bob needs one more hour to finish the lawn, this means it takes him 4 hours to cut it and therefore he cuts 1/4 of the lawn per hour.
Now, to know how much they cut by working together we need to sum up the amount of lawn they cut per hour:
Working together in one hour: Marsha's one hour + Bob's one hour
Working together in one hour: [tex]\frac{1}{3}+ \frac{1}{4}=\frac{4+3}{12}=\frac{7}{12}[/tex]
Therefore, working together they will cut 7/12 in one hour.
Now, to know how long will it take it to cut the entire lawn (which is equivalent to 12/12), we can write this in terms of proportions
Time Total amount of lawn
1 hour 7/12
x hours 12/12
Solving for x (to know the amount of hours it will take them) we have:
[tex]x=\frac{12}{12}[/tex]÷[tex]\frac{7}{12}[/tex]=[tex]1[/tex]×[tex]\frac{12}{7}=\frac{12}{7}=1.714[/tex]
Rounded to the nearest hundredth, we have that working together it will take them 1.71 hours to finish cutting the lawn.
