Dr Gulshan S. answered 15d
PhD In Physics and experience of teaching IB Physics and Math High sc
Using conservation of heat energy
Heat given out by Lead ball = Heat taken by water
Heat given by ball
Mass of Ball * Sp heat pf Lead* Fall in temperature
Heat taken by water = Mass of water* Sp heat of Water*Rise in Temp of water
Plug in values
3.8*159 * (Theta-26.8) = 2.5*4200*( 26.8-20.0)
Get value of Theta