Question

Please let me know if is it true?

If exactly 15 seconds of speech are to be sampled at a rate of 44 100
samples per second and each sample is represented by 16 bits of data,
then the resulting file size will be more than 1.4 megabytes.

Answer 1

so each sample takes 2 bytes ( 8 bits = 1 byte)

number of bytes = 15(44100)(2) = 1323000
= 1.26 MB

I divided by 1024^2 instead of 1000^2
Since 2^10 = 1024 , a number close to 1000, very often we estimate by using multiples of 1000 instead of the true power of 2.
If I use just multiples of 1000, then it would have been
1.32 MB

Here is a page with the different units
http://www.techeez.com/windows_tips/bits_in_a_byte.htm