For what value of k the following pair of linear equations has infinitely many solutions 10x 5y

For what value of k does the following pair of linear equations have no solution? 10x+5y k 5=0 and 20x+10y k=0.

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The given pair of linear equations are10x + 5y – (k – 5) = 0                  ……(i)20x + 10y – k = 0                           ……(ii)Which is of the form `a_1x + b_1y + c_1 = 0 and a_2x + b_2y + c_2 = 0`, where`a_1 = 10, b_1 = 5, c_1 = -(k – 5), a_2 = 20, b_2 = 10 and c_2 = -k`

For the given pair of linear equations to have infinitely many solutions, we must have

`(a_1)/(a_2) = (b_1)/(b_2) =(c_1)/(c_2)``⇒ 10/20 = 5/10 = (−(k−5))/(−k)``⇒ 1/2 = (k−5)/k`⇒ 2k – 10 = k ⇒ k = 10

Hence, k = 10.


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The given pair of linear equations are2x + 3y – 9 = 0                            ……(i)6x + (k – 2)y – (3k – 2) = 0           ……(ii)Which is of the form `a_1x + b_1y + c_1 = 0 and a_2x + b_2y + c_2 = 0`, where`a_1 = 2, b_1 = 3, c_1 = -9, a_2 = 6, b_2 = k – 2 and c_2 = -(3k – 2)`For the given pair of linear equations to have infinitely many solutions, we must have`(a_1)/(a_2) = (b_1)/(b_2) ≠ (c_1)/(c_2)``⇒ 2/6 = 3/(k−2) ≠ (−9)/(−(3k−2))``⇒ 2/6 = 3/(k−2) , 3/(k−2) ≠ (−9)/(−(3k−2))``⇒ k = 11, 3/(k−2) ≠ 9/((3k−2))`⇒ k = 11, 3(3k – 2) ≠ 9(k – 2)⇒ k = 11, 1 ≠ 3 (true)

Hence, k = 11.

The coach of a cricket team buys 3 bats and 6 balls for Rs. 3900. Later, she buys another bat and 3 more balls of the same kind for Rs. 1300. Represent this situation algebraically and graphically.

Let the cost of 1 bat be Rs. x and cost of I ball be Rs.y

Case I. Cost of 3 bats = 3x

Cost of 6 balls = 6y

According to question,

3x + 6y = 3900

Case II. Cost of I bat = x

Cost of 3 more balls = 3y

According to question,

x + 3y = 1300

So, algebraically representation be

3x + 6y = 3900

x + 3y = 1300

Graphical representation :

We have,    3x + 6y = 3900

⇒    3(x + 2y) = 3900

⇒    x + 2y = 1300

⇒    a = 1300 - 2y

Thus, we have following table :

For what value of k the following pair of linear equations has infinitely many solutions 10x 5y

We have,    x + 3y = 1300

⇒    x = 1300 - 3y

Thus, we have following table :

For what value of k the following pair of linear equations has infinitely many solutions 10x 5y

When we plot the graph of equations, we find that both the lines intersect at the point (1300. 0). Therefore, a = 1300, y = 0 is the solution of the given system of equations.

For what value of k the following pair of linear equations has infinitely many solutions 10x 5y