let f be the force of air resistance. for upward motion f acts downward.
let a1 be retardation
mg+f=ma1
for the downward motion f acts upward.
let a2=downward acceleration
mg-f=ma2
a2=g-f/m
thus, a1>a2
therefore t1<t2
because h=(a1.(t(to the power 2)))/2
also h=(a2.t2to thepower2)/2