Pump a can fill a tank in 12 minutes. Pump b can fill a tank in 20 minutes. How long to fill a tank with pump a and b together?

Rates add linearly, so together they are...

so 7 minutes, 30 seconds

A painter can finish painting a house in 6 hours Her assistant takes 8 hours to finish the same job How long would it take for them to complete the job if they were working together?

rates can be added:
1/6+1/8=1/t
4/24+3/24=1/t
1/t=7/24
t=24/7 =3 3/7 hr

Julie paints a house in 4 hours and Ken paints the same house in 5 hours. If they work together, they can paint the house in how many hours and minutes?

Work rates add linearly, so that:


1/4 +1/5 = 1/t
t=(4*5)/(4+5)=20/9


t= 2 2/9 hours



converting the fraction to minutes:
(2/9)*60= 13 1/3

1/3 of a minute is 20 sec, so...that the time is 2 hrs, 13 minutes and 20 sec

Ken mower can mow hi slawn in 20 minutes his son can do it in 12 minutes how long will it take if they do it together?

essentially we are to add: 
 

 minutes 


:)

Emily can paint her fence in 6 hours. If she does the job with her son, it take 2.5 hours less. How long would it take her son working alone.

Emily: 1/6 
son: 1/7 
together: 1/3.5 

so we can write: 

 

 
so her so can do it in 8.4 hours 


:)

A painter can paint a kitchen in 8 hours. An apprentice can paint the same kitchen in 24 hours. If they worked together, how long would it take them to paint the kitchen?

we can add their work rates, to solve for the time: 
1/t=1/8+1/24
1/t=3/24+1/24
1/t=4/24
t=6 

together they finish in 6 hrs

if one man paints a house in 3 hours and another man paints the same house in 5 hours, how fast can they paint the house together.

 
 
 

Two pipes can filIa tank in 10 hrs and 20 hrs, respectively. How long will they take to fill up the tank, if they are used together?

1/10+1/20 =1/t 
2/20+1/20 = 1/t 
3/20 = 1/t 
t=20/3 = 6 hrs 40 min 

:)

A brick layer takes 3/8 of MINUTE TO lay one brick. How many will he lay in 2 hrs?

he can lay... (2)(60)(8/3)=320 bricks

two computers can print out a task in 45 minutes and 30 minutes respectively. how long would it take to compete the task with both computers working together

C1: 1/45 
C2: 1/30 
together: 

 

 

18 minutes 


:)

Sue can sew a precut dress in 3 hours. Helen can sew the same dress in 2 hours. If they work together, how long will it take them to complete sewing that dress? Give your answer rounded to one decimal point if necessary

together: 
1/3+1/2=1/t 
t=(3x2)/(3+2)=6/5 

1 hr 12 min 

:)

Pipe A can fill a tank in 4 hours. If pipe B works alone it will take 3 hours longer than if both pipes worked together. How long will pipe B take if it works alone?

rate for A: 1/4
rate for B: 1/t
together: 1/(t-3) 
therefore 

 

then when we solve for t we get about 5.27 hrs 


:)