Solve the following system of equations by elimination method
6(ax + by) = 3a + 2b
6(bx - ay) =3b - 2a.
Let the initial salary be ‘x’ and increment per year be ‘y’
Case I. Initial salary = x
Increment after 4 years = 4y
According to question
x + 4y = 4500
Case II. Initial salary = x
Increment after 10 years = 10y
According to question
x + 10y = 5400
Thus, we have x + 4y = 4500 ...(i)
x + 10y = 5400 ...(ii)
Since the coefficient of ‘x’ in (i) and (ii) are equal.
So we can simply eliminate the variable ‘x’ by subtracting.
Putting this value in (i), we get
x + 4y = 4500
⇒ x + 4(150) = 4500
⇒ x + 600 = 4500
⇒ x = 3900
Hence, initial salary = Rs. 3900 and annual Increment = Rs. 150.
Problems Based on Cross-Multiplication Method
A motor boat whose speed is 24 km/h in still water takes 1 hour more to go 32km upstream than to return downstream to the same spot. Find the speed of the stream.
If the points A(k + 1, 2k), B(3k, 2k + 3) and C(5k – 1, 5k) are collinear, then find the value of k.