A pet shop has 7 guppy fish 13 tetra fish 5 angel fish David is going to choose one of the following combinations of fish a guppy fish and an angel fish or a tetra fish and an angel fish or a guppy fish, a tetra fish and an angel fish - Edexcel - GCSE Maths - Question 15 - 2022 - Paper 3

For the option of a tetra fish and an angel fish, we calculate:

• Number of ways to choose tetra fish: 13 (since there are 13 tetra fish)
• Number of ways to choose angel fish: 5 (since there are 5 angel fish)

The total combinations for this choice is: $13 imes 5 = 65$

For the combination of one guppy fish, one tetra fish, and one angel fish, we calculate:

• Number of ways to choose guppy fish: 7
• Number of ways to choose tetra fish: 13
• Number of ways to choose angel fish: 5

Thus, the total combinations for this choice is: $7 imes 13 imes 5 = 455$

Finally, we sum the total combinations from all choices:

$35 + 65 + 455 = 555$

Therefore, there are a total of 555 different ways for David to choose his fish.