Answer:
12
Step-by-step explanation:
The general formula for this is
Formula
1/t1 + 1/t2 = 1/t_tot
givens
t1 = 6 hours
t2 = x
t_tot = 4 hours
Solution
1/6 + 1/x = 1/4 Subtract 1/6 from both sides.
1/6-1/6 + 1/x = 1/4 - 1/6 Change to 12 as your common denominator
1/x = 3/12 - 2/12 subtract
1/x = 1/12 Cross multiply
x = 12
Tom would need 12 hours to do the job alone.
Answer:
Option D. 12 hours
Step-by-step explanation:
Let the work done by Tom to do the job alone = x hours
So per hour work done by Tom = [tex]\frac{1}{x}[/tex]
Jerry can do the job alone in the time = 6 hours
Per hour work done by Jerry = [tex]\frac{1}{6}[/tex]
Similarly job done by both together in the time = 4 hours
Per hour work done by both together = [tex]\frac{1}{4}[/tex]
Now we know,
Per hour work done by both together = per hour work done by Tom + Per hour work don by Jerry
[tex]\frac{1}{4}=\frac{1}{x}+\frac{1}{6}[/tex]
[tex]\frac{1}{x}=\frac{1}{4}-\frac{1}{6}[/tex]
[tex]\frac{1}{x}=\frac{3-2}{12}[/tex]
[tex]\frac{1}{x}=\frac{1}{12}[/tex]
x = 12 hours
Option D. will be the answer.
