SOLUTION: A boy bought two note books and two pens for Ghc 6.50. His sister bought one note book and two pens for Ghc 3.50. What was the cost of a note book and the cost of the pen.?

Question 1151616: A boy bought two note books and two pens for Ghc 6.50. His sister bought one note book and two pens for Ghc 3.50. What was the cost of a note book and the cost of the pen.?
Found 3 solutions by MathLover1, ikleyn, MathTherapy:
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
let the cost of a note book be and the cost of the pen
A boy bought note books and pens for Ghc .
......both sides divide by

......solve for
.............eq.1

His sister bought note book and pens for Ghc .
.....solve for
...........eq.2
from eq.1 and eq.2 we have
.....solve for

go back to
.............eq.1, substitute

the cost of a note book is and the cost of the pen is

Answer by ikleyn(52879)   (Show Source): You can put this solution on YOUR website!
.

            This problem is SPECIALLY INTENDED to solve it mentally in 2 minutes.

            This mental solution is as follows.

2 notebooks and 2 pens cost 6.50 1 notebook and 2 pens cost 3.50. It is totally clear from it (even for 3-rd grade student) that 1 notebook costs the difference 6.50-3.50 = 3 Ghc. Then two pens cost 3.50 - 3 = 0.50 Ghc. ANSWER. One notebook costs 3 Ghc. One pen costs 0.25 Ghc.

---------------

The lesson to learn from my solution is THIS :

Always read the condition attentively. It may happen that you can solve the problem mentally in two lines, instead of using and solving equations.

Answer by MathTherapy(10556)   (Show Source): You can put this solution on YOUR website!
A boy bought two note books and two pens for Ghc 6.50. His sister bought one note book and two pens for Ghc 3.50. What was the cost of a note book and the cost of the pen.?

Let cost of a pen be p, and a notebook, n
Then we get: 2n + 2p = 6.5_____2(n + p) = 2(3.25)____n + p = 3.25 ----- eq (i)
Also, n + 2p = 3.5 ------ eq (ii)
---- Subtracting eq (i) from eq (ii)
n + .25 = 3.25 ----- Substituting .25 for p in eq (i)

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