Pedagogy of Mathematics (Part II) - Algebra, Algebra, Maths, IX std Maths, Samacheerkalvi maths, II year B.Ed., Pedagogy, Mathematics, solving by cross multiplication method

1. PEDAGOGY OF
MATHEMATICS – PART II
BY
Dr. I. UMA MAHESWARI
Principal
Peniel Rural College of Education,Vemparali,
Dindigul District
iuma_maheswari@yahoo.co.in

2. STD IX
CHAPTER 3 – ALGEBRA
Ex – 3.13

11. (i) 8x – 3y = 12; 5x = 2y + 7
Solution:
8x – 3y – 12 = 0 → (1)
5x – 2y – 7 = 0 → (2)
Use the coefficients for cross multiplication

12. x/−3 = -1 ⇒ x = 3
y/−4 = -1 ⇒ y = 4
∴ The value of x = 3 and y = 4

13. (ii) 6x + 7y – 11 = 0; 5x + 2y = 13
Solution:
6x + 7y – 11 = 0 → (1)
5x + 2y = 13 → (2)
Use the coefficient for cross multiplication

15. Solution:
Let the number of 2 rupee coins be “x” and the number of 5 rupee coins be “y”.
By the given first condition
x + y = 80 → (1)
Again by the given second condition
2x + 5y = 220 → (2)
x + y – 80 = 0 → (3)
2x + 5y – 220 = 0 → (4)
Using the coefficients for cross multiplication