Question

Cost of 8 pencils, 5 pens and 3 erasers is rs 111. Cost of 9 pencils, 6 pens and 5 erasers is rs 130. Cost of 16 pencils, 11 pens and 3 erasers is rs 221. What is the cost (in rs) of 39 pencils, 26 pens and 13 erasers?

Answer 1

Answer:

Follow The Steps and Get answer by yourself

Step-by-step explanation:

8x+ 5y+ 3z = 111

9x+ 6y+ 5z = 130

16x+ 11y+ 3z = 221

Form a Matrix,

8    5    3    111    -----1

9    6    5    130   -----2

16   11   3    221   -----3

Row 2 = 3*R2 - 5*R1

Row 3 = R3 - R1

8    5    3    111    -----1

-13  -13  0   -165 -----2

8    6    0    110   -----3

Row 3 = 13*R3 + 6*R2

8    5    3    111

-13  -13  0    -165

26  0    0    440

Therefore, 26x = 440

x = 440/26 = 17

-13(17) - 13y = -165

221 + 13y = 165

13y = 165-221 = -56

y = -4

8(17) + 5 (-4) + 3z = 111

136 - 20 + 3z = 111

3z = 111 - 116

3z = -5

z = -1.6

Substitute x, y and z in the desired equation to get the answer.

Steps are correct. But the answer shown here is wrong.

Always follow Matrix meth0d when solving 3 Quadratic Equation having 3 Unknowns.