One bricklayer can build a wall in 6 hours. another bricklayer could build the same wall in 4 hours. if they work together, how long will it take to build the wall?

Hello,

Let's

V1 the velocity of the 1st bricklayer,

V2 the velocity of the 2nd bricklayer,

1wall=V1*6==>V1=w/6

1wall=V2*4==>V2=w/4

==>V1+V2=w/6+w/4=10w*24=5w/12

Let's t the time for the 2 bricklayer to build the wall

(V1+V2) t=w

==>5w/12*t=w

==>t=12/5 (h) = 2h24min.