A body of mass 2kg makes an elastic collision with a second body at rest and continues to move in the original direction but with one fourth of its original speed. What is the mass of the second body?

Correct option is B. 1.2kg
By conservation of linear momentum
2v₀ = 2(v₀/4) + mv → 2v₀ = v₀/2 + mv → (3v₀)/2 = mv (1)
Since collision is elastic
vseparation = vapproach → v - v₀/4 = v₀ → (5v₀)/4 = v
Equating (2) and (1)
(3v₀)/2 = m((5v₀)/4) → m = 6/5 = 1.2kg