Question

Rohini had scored 10 more marks in her mathematics test out of 30 marks, 9 times these marks would have been the square of her actual marks. How many marks did she get on the test?

Options

• 14 

• 16

• 15

• 18

Answer 1

15

Explanation:

Let her actual marks be x.

Therefore,

9 (x + 10) = x²

⇒ x² – 9x – 90 = 0

⇒ x² – 15x + 6x – 90 = 0

⇒ x(x – 15) + 6 (x – 15) = 0

⇒ (x + 6) (x – 15) = 0

Therefore x = – 6 or x = 15

Since x is the marks obtained, x ≠ – 6. Therefore, x = 15.