In △ABC, D, E and F are the midpoints of sides AB, BC and CA, respectively. If AB = 12 cm, BC = 20 cm and CA = 15 cm, then the value of $\frac{1}{2}$(DE + EF + DF) is:

11.75 cm

 D, E and F are the midpoints of sides AB, BC and CA, respectively.

So, ( DE +  EF + DF ) = \(\frac{1}{2}\) × (AB + BC + CA )

= \(\frac{1}{2}\) × (12 + 20 + 15  )

= \(\frac{1}{2}\) × (47 )

= 23.5

Now,  \(\frac{1}{2}\) × ( DE +  EF + DF ) = \(\frac{1}{2}\) × 23.5

= 11.75 cm