Math doubts - help

1) y km/hr = y * 1000 m/60*60 s = 5y/18 m/s = x m/s

So y = 18x/5

2) y=3x+2....now if a point (r,s) is present in the line then this equation has to be satisfied for that point...ie s=3r+2 has to be satisfied or 3r-s+2 = 0

Now if u see in both stmts we have prod of 2 equations equalled to 0 which means any of terms can be zero. If we combine them we can get 3r-s+2 = 0....Ans is C

Sorry but didn't understand the second answer...

if a point lies in and equation then that equation has to be satisfied with the value of the co-ordinates of that point....u can take any linear equation and verify using different values of co-ordinates. In our case if the point (r,s) lies on the line y=3x+2 then s=3r+2 or 3r-s+2 = 0....i hope u have understood this part. Now we need to prove whether 3r-s+2 is 0 or not

stmt 1 - expression 1 * expression 2 = 0 which means either expression can have a value of 0. So insuff

Stmt 2 - same explanation as stmt1....any expression can have a value 0...so insuff

both - we can see that only one expression is in common and that is 3r-s+2 and this has to be zero for both expressions to be zero....So ans is C..

Of course... got it....

tnks a lot