question on rates (1 Viewer)

[xtrant]

hi,
this is going to be a very simple question and i think i know the answer but i just don't know the reasoning behind it.
sam lays 150 bricks in 60 mins and kevin lays 20bricks in 10mins. working together, how many minutes will it take sam and kevin to lay 180 bricks?
btw, this is a yr4/5 question so im not proud to say that i dont know how to reason it but at least ill learn from it
thanks for the help!

 

[shuning]

回复: question on rates

t(150/60) + t(20/10) = 180
solve for t

40min
am i wrong?

 

[xtrant]

Re: 回复: question on rates

nah thats right! thanks for that!