Two factory plants are making TV panels. Yesterday, Plant A produced 3 times as many panels as Plant B. Three percent of the panels from Plant A and 4% of the panels from Plant B were defective. How many panels did Plant A produce, if the two plants together produced 1300 defective panels?

Let us assume the number of panels produced by Plant A = z

Let us assume the number of panels produced by Plant B = y

Then

x = 3y

0.03x + 0.04y = 1300

Multiplying both sides of the second equation by 100, we get

3x + 4y = 130000

Putting the value of x from the first equation in the second equation, we get

3x + 4y = 130000

3 (3y) + 4y = 130000

13y = 130000

y = 10000

Then

x = 3 * 10000

= 30000

From the above deduction, we can conclude that the number of panels made by Plant A is 30000.