25. tom and jerry must stuff and mail 1000
envelopes for a new marketing campaign. jerry
can do the job alone in 6 hours. if tom ,
they can get the job done in 4 hours. how long
would it take tom to do the job by himself?
a. 4 hours
b. 5 hours
c. 8 hours
d. 12 hours

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.

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 =

Jerry can do the job alone in the time = 6 hours

Per hour work done by Jerry =

Similarly job done by both together in the time = 4 hours

Per hour work done by both together =

Now we know,

Per hour work done by both together = per hour work done by Tom + Per hour work don by Jerry

x = 12 hours

Option D. will be the answer.