m1*c*(to-t1) + m2*c*(to-t2) = 0
to = (m1*t1+m2*t2)/(m1+m2) = (1000*20 + 100*100)/(1000+100) = 27.27 °C
m1*c*(to-t1) + m2*c*(to-t2) = 0
to = (m1*t1+m2*t2)/(m1+m2) = (1000*20 + 100*100)/(1000+100) = 27.27 °C