Please help with my Maths?

Question

I'm struggling with this one!

The deflection y of a circular plate suspended at it's circumference is given by

y=Awd^4/t^3

where w is the load on the plate, t is the thickness d is its diameter. If t drops by 2%, w increases by 3% and d drops by 1.5% find the percentage change in y.

Answer 1

yo = Awd^4/t^3

and y1 = A[1+0.03]w[1-0.015]^4d^4/[1-0.02]^3t^3

y1 = 0.944160560276875Awd^4/0.941192t^3

y1 ~ 1.003Awd^4/t^3

the percentage change in y = [(y1-y0)/y0]x100%

the percentage change in y ~ 0.003 x 100% ~ 0.3% only