9514 1404 393
Answer:
20th
Step-by-step explanation:
The person will receive all gifts if the are all of a multiple of 2, a multiple of 4, and a multiple of 5. Since 4 is already a multiple of 2, the person who will receive all is the one who is a multiple of 4 and 5.
20 is 4×5, so is a multiple of both numbers. There is no smaller number that is a multiple of both 4 and 5.
The 20th person will receive all gifts.
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The value we have determined here is called the "least common multiple" (LCM). It is the product of the unique prime factors of the numbers of interest, raised to the highest power that appears in any of the numbers.
2 = 2¹
4 = 2²
5 = 5¹
LCM(2, 4 5) = 2² × 5¹ = 20
