Machine A      60 mins      u  cards

Machine B       90mins      u  cards

Machine A         1 min    —–>  u/60 cards

Machine B         1 min    —–>  u/90 cards

(u/60) – (u/90) = 8

(3u-2u)/180 = 8

u = 8 x 180 = 1440

Therefore total cards printed by both machines are 1440 x 2 = 2880

Lol.  I almost got the same answer as you except I missed the “8 cards PER MINUTE” statement.  I thought it was 8 cards total and was puzzling how to get speed to be equal to a number 8.

Sigh.  Well done!

Chief,

Their main aim is to trick the mind….so..must read carefully lor…   Some tricks are really badly set…like the footpath one in the field…  why confuse drawing and words?   In real life problems, we can clarify by asking but in exam, how would the invigilator know?   So while they want to be creative to trick the mind, it would be necessary to be reasonable.  They really should vet the questions properly before releasing it for exams to be absolutely fair.