Two spherical camphor particles of radii 20 cm and 5 cm, far away from each other, are undergoing sublimation in a stream of air. The mass transfer coefficient is proportional to 1/√r(t), where r(t) is the radius of the sphere at time t. Assume that the partial pressure of camphor far away from the surface of the particle is zero. Also, assume quasi-steady state, identical ambient conditions, and negligible heat effects. If t₁ and t₂ are the times required for complete sublimation of the 20 cm and 5 cm camphor particles, respectively, the ratio t₁/t₂ is ______ (rounded off to one decimal place).