There are three earning members in a
family - Mr Roy, Mrs Roy and their daughter Teena. the average monthly
income of Mr and Mrs Roy is 5050.,
whereas the average monthly income of
Mrs Roy and Teena is 6250. The average monthly income of Mr Roy and
Teena is 5200. What is Mr Roy's income ( with full steps )

solution :

Let the monthly income of Mr Roy(in Rupees) = x

Let the monthly income of Mrs Roy(in Rupees) = y

Let the monthly income of Teena (in Rupees)= z

according to question ,

x+y/2 = 5050

or x+y =5050*2

or** ****x+y =10100.............. (1st)**

the average monthly income of
Mrs Roy and Teena is 6250

y+z / 2 = 6250

y+z=2*6250

y+z=12500----------------------(2nd)

average monthly income of Mr Roy and
Teena is 5200.

x+z /2= 5200

x+z= 2*5200

**x+z =10400--------------------(3rd)**

subtract 3rd from 1st , we get

x+y - (x+z)=10100 - 10400

x+y -x -z = -300

y-z = -300

or** y= z- 300**

substitute y = z - 300 in equation 2nd , we get

z- 300 + z = 12500

2z =12500+300

2z = 12800

or z = 12800/2

** z= 6400**

Hence Teena's monthly income is rupees 6400.

Substitute z= 6400 in 3rd equation ,

x+z=10400

x+6400 =10400

x=10400 -6400

x=4000

**Therefore , Mr Roys monthly income is Rs 4000**

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