Math, asked by graj33228, 23 hours ago

Raghav, Chandni, and Sohum purchased pens, erasers, and pencils. Raghav said, “Seven pens and five erasers cost the same as six pencils. Chandni said, "Four pens and nine pencils cost the same as five erasers. Sohum said, " cost of six pencils and three erasers is the same as four pens. It seems that one of them has made the wrong statement. Who committed error in calculations and gave the wrong statement? ​

Answers

Answered by amitnrw
3

Given : Raghav said,  Seven pens and five erasers cost the same as six pencils.

Chandni said, "Four pens and nine pencils cost the same as five erasers.

Sohum said, " cost of six pencils and three erasers is same as four pens

one of them has made wrong statement

To Find : Who committed error in calculations

Solution:

Pen cost = x

Pencil cost = y

eraser cost = z

Raghav said,  Seven pens and five erasers cost the same as six pencils.

=> 7x + 5z  = 6y

Chandni said, "Four pens and nine pencils cost the same as five erasers.

=> 4x + 9y = 5z

Sohum said, " cost of six pencils and three erasers is same as four pens

=> 6y + 3z  = 4x

Case 1 :  Assume Raghav did not make error

Raghav

7x + 5z  = 6y => 5z = 6y - 7x    

Chandni

4x + 9y = 5z

Substituting  5z  from raghav

=> 4x + 9y = 6y - 7x

=> 11x + 3y = 0    which is not possible

Hence Chandni  made error

Sohum  

6y + 3z  = 4x

Substituting   6y  from raghav

7x + 5z +  3z  = 4x

=> 8z + 3x = 0  which is not possible

Hence Sohum   also made error

so This case is not possible as 2 person made error.

so Raghav must have made error

Still lets check all possible cases to verify

Case 2 :  Assume Chandni  did not make error

Chandni  

4x + 9y = 5z      => 4x = 5z - 9y

Raghav

7x + 5z  = 6y

substitute 5z from Chandni

7x + 4x + 9y = 6y

=> 11x + 3y = 0   which is not possible

Hence Raghav  made error

Sohum  

6y + 3z  = 4x

Substituting   4x  from  Chandni

6y +  3z  = 5z - 9y

=> 15y = 2z    which is  possible

Hence only Raghav  made error

So this is possible that Raghav made an error

Case 3 :

Sohum did not make error

6y + 3z  = 4x    => 6y = 4x - 3z

Raghav :

7x + 5z  = 6y

substitute 6y from  Sohum

=>  7x + 5z = 4x - 3z

=> 3x + 8z = 0  which is not possible

Hence Raghav  made error

Chandni

4x + 9y = 5z

substitute 4x from  Sohum

6y + 3z + 9y = 5z

=> 15y = 2z  which is  possible

Hence Raghav has made error

Raghav Committed error in calculations

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