Permutations and Combinations: Arrangement of Identical Cans

Published on September 25, 2026

Word-Problem

Calculate the number of arrangements for 7 identical cans under specific conditions by treating groups of identical items as single blocks. The solution covers both restricted end positions and grouped item constraints.

Question

Answer

Since you haven’t specified which problem you would like me to solve, I will solve Problem 10, as it is circled in your image and has handwritten notes.

Problem 10

Three identical cans of cola ( ), 2 identical cans of green tea ( ), and 2 identical cans of orange juice ( ) are arranged in a row. Calculate the number of arrangements if:
(i) the first and last cans in the row are the same type of drink.
(ii) the 3 cans of cola are all next to each other and the 2 cans of green tea are not next to each other.

Solution

Total number of cans = cans.

Part (i): The first and last cans are the same type of drink.

We consider three mutually exclusive cases based on which type of drink is at both ends.
Case 1: Both ends are Cola ( )
Remaining cans to arrange in the middle: (Total 5 cans).
Number of arrangements = .
Case 2: Both ends are Green Tea ( )
Remaining cans to arrange in the middle: (Total 5 cans).
Number of arrangements = .
Case 3: Both ends are Orange Juice ( )
Remaining cans to arrange in the middle: (Total 5 cans).
Number of arrangements = .
Total for (i) .

Part (ii): The 3 cans of cola are all next to each other and the 2 cans of green tea are not next to each other.

Step 1: Treat the 3 colas as a single block.
Let the block of colas be .
The items to arrange are now: (Total 5 items).
Step 2: Calculate arrangements where is present, ignoring the restriction on .
Total arrangements of .
Step 3: Subtract arrangements where the 2 green teas ( ) are next to each other.
Treat the two green teas as a single block .
The items to arrange are now: (Total 4 items).
Number of arrangements of .
Step 4: Final calculation for (ii).
Number of arrangements = (Total with ) (Arrangements where are together)
Number of arrangements .

Final Answers:
(i) 50
(ii) 18