Question 214819
Five pens of the same type cost the same as two notebooks of the same type. If one pen and two notebooks cost $4.20, what is the cost of one pen?


Step 1.  Let x be the cost of one pen.  Let y be the cost of a notebook.


Step 2.  Let 5x be the cost of 5 pens.


Step 3.  Let 2y be the cost of 2 notebooks.


Step 4.  Then, 5x=2y since the cost of 5 pens is the same as the cost of two notebooks.


Step 5.  x+2y=4.20 as given by the problem statement


Step 6.  Substitute 5x=2y of Step 4 into Step 5.  Then 


{{{4.20=x+2y=x+5x=6x}}}


Divide by 6 on both sides of equation.


{{{4.20/6=6x/6}}}


{{{0.70=x}}}


{{{x=0.70}}}  cost of one pen.


And {{{2y=5x=3.50}}}  cost of two pens


Also, {{{x+2y=0.70+3.50=4.20}}} cost of one pen and two notebooks


Step 7.  ANSWER:  Cost of one pen is $0.70


I hope the above steps were helpful.


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Good luck in your studies!


Respectfully,
Dr J