Question

P varies directly as q. When q = 31.2, p = 20.8. Find p when q = 15.3.

Answer 1

P = kq   where k is a constant
Substituting:-
20.8  = 31.2 * k
k = 20.8 / 31.2 = 0.6667
so the relation is p = 0.6667q

When q = 15.3
P  = 0.6667*15.3 =  10.20   to nearest hundredth

Answer 2

31.2/20.8=15.3/p
p=(20.8*15.3)/31.2
p=10.2