Are Following Numbers In Proportion 32 40 48 And 60

Are the following numbers in proportion: (i) 32, 40, 48 and 60 ? (ii) 12,15,18 and 20 ?

(i) 32, 40, 48 and 60 are in proportion
if 32 : 40 = 48 : 60
if 32 x 60 = 40 x 48
$\left\{ \frac { a }{ b } =\frac { c }{ d } \Longrightarrow \quad ad=bc \right\}$
if 1920 = 1920
Which is true.
32, 40, 48 and 60 are in proportion
(ii) 12, 15, 18 and 20 are in proportion
if 12 : 15 = 18 : 20
if 12 x 20 = 15 x 18 {ad = bc}
if 240 = 270
which is not true.
12, 15, 18 and 20 are not in proportion.