A card is drawn randomly three times from the deck of cards with replacement. If the probability of getting spade cards all three times is $k$ then $16k=$

There are 13 spade cards in the deck of playing cards.

hence, the probability of getting one spade card from the deck of cards is $\frac{13}{52}=\frac{1}{4}$

Since, the card drawn randomly three times with replacement, the events of getting spade cards each time are independent

Therefore, 

            $\begin{array}{rcl}k& =& \frac{1}{4}·\frac{1}{4}·\frac{1}{4}\\ & =& \frac{1}{64}\end{array}$

It implies that $16k=\frac{16}{64}=\boxed{0.25}$