When we combine the three gas laws into one expression:

Question

V is directly proprtional to T
P is directly propetional to T ---------> PV is directly proprtional to T
P is inversely proportional to 1/V

PV/T= constant

*******I do not understand how PV is directly proportional to T and how PV/T= constant. Is there a mathematical manipulation or something? Please explain.

Answer 1

PV=nRT replacing nR with c,a constant, then PV=cT

so PV is directly proportional to T

for part 1, divide
PV=cT by T
PV/T=constant