The angle between two straight lines having direction cosines l21,m21,121  and  354,354,3l54  is 900, then a pair of possible values of l,m respectively are

If the direction ratios of two perpendicular lines are proportional to  a1,b1,c1,a2,b2,c2 then  a1a2+b1b2+c1c2=0Hence  l21⋅354+m21⋅354+121⋅3l54=0It implies that  6l+3m=0⇒2l+m=0Verify the options for suitable values of l,m