Home » Aptitude » Ratio, Proportion » Question
  1. If (x3 – y3) : (x2 +xy +y2) = 5 : 1
    and (x2 – y2) : (x – y) = 7 : 1, then the ratio 2x : 3y equals
    1. 4 : 1
    2. 2 : 3
    3. 4 : 3
    4. 3 : 2
Correct Option: A

x3 − y3
=
5
x2 + xy + y21

⇒ 
(x − y)(x2 + xy + y2)
= 5
x2 + xy + y2

⇒   x – y = 5       ....(i)
Again,
x2 − y2
= 7
x − y

⇒ 
(x + y)(x − y)
= 7
x − y

⇒   x + y = 7       ....(ii)
On adding equations (i) and (ii),
2x = 12 ⇒ x = 6
From equation (ii),
x + y = 7 ⇒ y = 7 – 6 = 1
∴ 
2x
=
2 × 6
= 4 : 1
3y3 × 1



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