1 L of 20 degrees C water is mixed with 4 L of 40 degrees celcius water. What will be the temp of this mixture?

the only thing i know is like
V/T = V/T but im not sure how it relates to this problem, if at all.

1L*20C+4L*40C=5L*??

solve for ??

20+160=5??
??? = 180/5 or 36C