The apparent weight of a person inside a lift is 'W1'.when lift moves up with certain acceleration and is w2.when lift moves down with same acceleration.The weight of person when lift moves up with constant speed is

see now we have when the lift is moving down with constant acceleration upwards we get the equation as

mg-ma=w1....(1)

and when moving up with same acceleration we get w2,

so mg+ma=w2....(2);

now while the lift is moving down with constant speed there is n external force except the gravitational force so then we will get the weight of the person

that is (1)+(2)

mg - ma + mg + ma = w1 +w2

we get 2mg = w1+ w2

so weight of the person is (w1 + w2)/2.