How much the temperature of a brass rod ( ὰ = 0.00002 ⁰C^-1 ) be increased so as to increase its length by 1% ?

We will use the following formula

dl / l = α_l.dT 

here dl/l = 0.01

α_l = 0.00002 /^oC

so,

dT = (dl / l).(1/α_l)

thus,

dT = 0.01 / 0.00001

so, the increase in temperature will be

dT = 500^oC