Question

If p is directly proportional to q and if p = 14 when q = 8, what is the value of p when q = 28

Answer 1

p=34 although that may not be right

Answer 2

14/8 = p/28
cross multiply
(8)(p) = (28)(14)
8p = 392
p = 392/8
p = 49

check..
14/8 = 49/28
cross multiply
(8)(49) = (28)(14)
392 = 392 (correct)

p = 49 when q = 28

Answer 3

you may do like this also.
If p is directly proportional to q, then p=k q
If p is inversely proportional to q,then p=q/k
where k is a constant.
14=8k,k=14/8=7/4
\[p=\frac{ 7 }{4 }q,when q=28,p=\frac{ 7 }{4}*28=49\]