If two cards are taken one after another without replacing from a pack of 52 cards. What is the probability for the two cards be Ace ?

Total Combination of getting a card from 52 cards =  $C152$

Because there is no replacement, so number of cards after getting first card= 51

Now, Combination of getting an another card=  $C151$

Total combination of getting 2 cards from 52 cards without replacement= ( $C152\times C151$) 

There are total 4 Ace in stack. Combination of getting 1 Ace is =  $C14$

Because there is no replacement, So number of cards after getting first Ace = 3

Combination of getting an another Ace =  $C13$

Total Combination of getting 2 Ace without replacement= $C14\times C13$

Now,Probability of getting 2 cards which are Ace = $\frac{C14\times C13}{C152\times C151}$ = 1/221.