TIPS for calculating math faster(1)

how we calculate mentally these numbers faster?
example:
1. 14 x 12 = ...?
method: ( try to visualize this in mind)
i) add 2 to 14 = 16, u write it as 160
ii) multiply 2 by 4 = 8
iii) 160 + 8 = 168
so 14 x 12 = 168

2. 16 x 15 = ...?
method:
i) add 5 to 16 = 21, u write it as 210
ii) multiply 5 by 6 = 30
iii) 210 + 30 = 240
so 16 x 15 = 240.
easy right?
try with other numbers!
is there any limitation for this technique?
all the best for you!!!