There are different ways to approach this problem, but one possible method is to use combinations. Pita can take out 3 coins out of 12 in 12C3 = 220 ways (i.e., the number of combinations of 3 items from a set of 12). To calculate the probability of taking out exactly £2.50, we need to count the number of combinations that contain 2 of the £1 coins and 1 of the 50p coins.
There are 3C2 = 3 ways to choose 2 of the £1 coins, and 9C1 = 9 ways to choose 1 of the 50p coins. The number of combinations that contain 2 of the £1 coins and 1 of the 50p coins is therefore 3 x 9 = 27.
The probability of taking out exactly £2.50 is therefore 27/220, which can be simplified to 3/22 or approximately 0.1364 (rounded to four decimal places).