An inkjet printer can print 8 lines/second and can print a document in 6 minutes. How much time would an LED printer take to print the same document if it can print 7 lines/second more than the inkjet printer?

An inkjet printer can print 8 lines/second and can print a document in 6 minutes.

1 minutes = 60 seconds

6 minutes = $$60\times6$$ seconds = 360 seconds

Total lines in the document = $$8\times360$$

= 2880 lines   Eq.(i)

LED printer takes to print the same document if it can print 7 lines/second more than the inkjet printer.

Speed of LED printer = 8+7 = 15 lines/second    Eq.(ii)

time taken by LED printer to print the document = $$\frac{Eq.(i)}{Eq.(ii)}$$

= $$\frac{2880}{15}$$

= 192 seconds

= $$\frac{192}{60}\ minutes$$

= $$3\frac{12}{60}\ minutes$$

= 3 minutes 12 seconds