Terry can paint a house in 45 hours. His father can paint the same house in 50 hours and his brother can paint it in 40 hours. How long will it take all three working together to do the painting? Help please? I need the solution. THANKS!

Question

amistre64 · Answer

How much can they each do in 1 hour alone?

amistre64 · Answer

Terry takes 45 hours to do the whole thing; so 45/45 is complete for him.  How much is done in 1 hour?  1/45 right?

amistre64 · Answer

Dad can do it all in 50 hours:  50/50 is complete for him.  How much is done in 1 hour?

anonymous · Answer

And the brother can do it in 40/40.

amistre64 · Answer

good; so each one alone can do: 1/45  +  1/50  + 1/40, we have to add all those fractions together to be able to solve this now

anonymous · Answer

then..

anonymous · Answer

1800/141

anonymous · Answer

Can u see how ?

amistre64 · Answer

lol .... yeah; I get 121/1800 after adding.

then flip it over like rosh has done to get the answer

anonymous · Answer

no. :'(

anonymous · Answer

okay. so the answer is 1800/141?

anonymous · Answer

Yeap

anonymous · Answer

In one hour terry can paint 1/45 house Similarly father and brother in 1/50 and 1/40 house respectively
So in one hour all can paint 1/45 + 1/50 + 1/40

anonymous · Answer

how can i convert it in time? i cant answer 1800/121. the answer should be in hours right?

anonymous · Answer

which will give you 141/1800, now just flip it over to get the answer

anonymous · Answer

12.76 hours

anonymous · Answer

sorry should have been 1800/121

anonymous · Answer

I screwed up on adding LOL, 14.88 hours

amistre64 · Answer

first we get common denominators:  I think 5 is a good common denominator ... maybe :)

 1/9         1/10        1/8       1/9 + 1/10 + 1/8
---- +   ------ +  ----- =  ----------------
45/9      50/10       40/8                  5

Now that the numbers are smaller :)  we can find a common denominator of 9,10, and 8;  360 pops out in the end.

1*40    1*36      1*45       40+36+45       121
---- + ----- + ----- =  ---------- =  ------
9*40    10*36     8*45           360              360


Now that that is over; lets use it

121/360        121          121
-------- =  ------ =  ------ ; yay!!
     5             5*360       1800

anonymous · Answer

THANK YOU! GOT IT ALREADY. SO HELPFUL!

amistre64 · Answer

Since there is 1800 "parts" to paint; and 121 get painted in an our we get:

121*hours = 1800

hours = 1800/121 ; which is just the flipped version of what we got prior

anonymous · Answer

Well done amistre64  Ha Ha

amistre64 · Answer

;) thanx