Using Quadratic Formula to solve Quadratic Equations
Ncert Solutions Chapter 4 Quadratic Equations Exercise 4.3 Q5 Download this solution
5. In a class test, the sum of Shefali’s marks in Mathematics and English is 30. Had she got 2 marks more in Mathematics and 3 marks less in English, the product of their marks would have been 210. Find her marks in the two subjects.
Solution:
Let Shefali’s marks in Mathematics =
Let Shefali’s marks in English =
If, she had got 2 marks more in Mathematics, her marks would be =
If, she had got 3 marks less in English, her marks in English would be =
=
According to given condition:
Comparing quadratic equation
with general form
, we get
and
Applying Quadratic Formula
, we get
Therefore, Shefali’s marks in Mathematics = 13 or 12
Shefali’s marks in English =
Or
Shefali’s marks in English =
Therefore her marks in Mathematics and English are
or
.
gwrgwrrrrrrrrrrr says
i think in this line
⇒27x−x2+54−2x=210
⇒x2−25x+156=0
there should be -156 instead of 156
Jashan says
Please read carefully. It has to be +156 because terms are moving to the right hand side.