Let weight of a chocolate bar, and a packet of candy, be B, and C, respectively

Then we get: 3B + 4C = 200 ------ eq (i)

Also, 3B + 7C = 260 ------ eq (ii)

3C = 60 ------ Subtracting eq (i) from eq (ii)

Weight of a chocolate bar, or 

Substitute 20 for C in either eq (i) or eq (ii) and solve for B to get the weight of a chocolate bar.



If you love to TORMENT yourself, then you can do the problem the way the other person did. 

I have no idea why she continues to make MOUNTAINS out of MIOLEHILLS with these simple-enough math problems. 

Answer by ikleyn(52797)   (Show Source): You can put this solution on YOUR website!
 .

3 similar chocolate bars and 4 similar packets of candy weigh 200 g. 

3 such    chocolate bars and 7 such    packets of candy weigh 260 g. 

What is the weight of a chocolate bar?

~~~~~~~~~~~~~







            Actually,  this problem is intended for  MENTAL  solution without using equations.







Looking into the text, an attentive reader sees that


    - the difference between two purchases is 3 packets of candy

    - and the difference in weights between two purchases is 260-200 = 60 grams.


Hence, the weight of one packet of candy is   60/3 = 20 grams.


From it, the weight of 3 chocolate bars is  200 - 4*20 = 120 grams.


Hence, each chocolate bar weights  120/3 = 40 grams.




Solved.





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





To see many other similar  (and different)  problems,  solved in the same way,  look into the lesson



    - Solving mentally word problems on two equations in two unknowns 



in this site.





Also,  you have this free of charge online textbook in ALGEBRA-I in this site



    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.





The referred lesson is the part of this online textbook under the topic "Systems of two linear equations in two unknowns".







Save the link to this online textbook together with its description





Free of charge online textbook in  ALGEBRA-I

https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson





to your archive and use it when it is needed.







 

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