Answer: The least number of packages of caps and shirts that need to be ordered is 15 and 9 respectively.
Explanation:
Given : The science club sponsors are ordering caps and shirts for the boys and girls in the science club.
Number of science club members = 45
The caps come in packages of 3 and the shirts come in packages of 5 .
The least common multiple of 3 and 5 =

[∵
]
Also,
i.e. 45 is a multiple of 15 and the number of science club members is 45.
Now, the least number of packages of caps needed =

and the least number of packages of shirts needed =

Hence, the least number of packages of caps and shirts that need to be ordered is 15 and 9 respectively.