RRB NTPC Mains or Stage 2 Model Paper 7 with solutions

(b) Given,

3

x+y

+

2

x–y

=2     ... (i)
and

9

x+y

−

4

x–y

=1     ... (ii)
Let

1

x+y

=a and

1

x–y

=b
∴ 3a + 2b = 2   ... (iii)
9a – 4b = 1   ... (iv)
On multiplying equation (iii) by 2 and addition of equation (iv) and new one, then we get
6a+ 4b= 419a – 4b= 1
_________
15a  = 5
⇒a=

5

15

=

1

3

⇒

1

x+y

=3   ... (v)
On putting the value of (a) in equation (iii),we get
3×

1

3

+2b=2
⇒ 2b = 2 – 1 = 1
⇒b=

1

2

⇒

1

x–y

=

1

2

⇒ x – y = 2... (vi)
∴x +y =3
x – y =2
______
2x   =5
⇒x=

5

2

From equation (v),
y=3–

5

2

=

1

2

∴

x

y

=

5 2 1

2

=5