Final answer:
Mr. Gan could have 7, 10, 13, or 16 candies.
Step-by-step explanation:
Let's assume that Mr. Gan has x candies.
If he packs 3 candies in each bag, he will have 4 extra candies left over. This means that the total number of candies can be expressed as 3n + 4, where n is the number of bags. Since we know that Mr. Gan has fewer than 20 candies, we can set up the inequality:
3n + 4 < 20
Solving this inequality, we find that n < 5.
If he packs 5 candies in each bag, he will be short of 2 candies. This means that the total number of candies can be expressed as 5m - 2, where m is the number of bags. Using the same reasoning, we can set up the inequality:
5m - 2 < 20
Solving this inequality, we find that m < 4.
Combining the two inequalities, we know that n < 5 and m < 4. Since n and m represent the number of bags, they must be positive integers. So the possible values for n are 1, 2, 3, and 4, and the possible values for m are 1, 2, and 3.
If we substitute these values into the equations, we can find the corresponding number of candies:
If n = 1, then 3n + 4 = 7 candies.
If n = 2, then 3n + 4 = 10 candies.
If n = 3, then 3n + 4 = 13 candies.
If n = 4, then 3n + 4 = 16 candies.
If m = 1, then 5m - 2 = 3 candies.
If m = 2, then 5m - 2 = 8 candies.
If m = 3, then 5m - 2 = 13 candies.
Since Mr. Gan has fewer than 20 candies, the only possible values for the number of candies he has are 7, 10, 13, and 16.