Answer:It started at 20°C, the bras and the iron must b cooled at -150°C.
Step-by-step explanation:
The formular for linear expansion is given by:
L = Lo + Lo&◇T
Where L = linear dimensions)diameter) after temperature change.
Lo=Original linear dimension
&= Coefficient of thermal expansion for the material.
◇T=Change in temperature.
At some temperature,L(brass)=L(iron)
Lo + Lo&◇T = Lo + Lo&◇T
8.753cm + 8.753cm×(8.7×10^-6C^-1)×◇T=8.753cm+ 8.753cm ×(12.0×10^-6C^-1)×◇T
8.753+(1.636×10^-4)◇T= 8.753+(1.049×10^-4C^-1)◇T
5.87 × 10^-5◇T= 0.010
◇T= 0.010/(5.87×10^-5)
◇T= 170°C
◇T=T1-T2
T= (20 - 170)°C
T= -150°C