Question

One chicken lays an egg every 2 days, another every 3 days and a third chicken lays an egg every 5 days. They all lay an egg today. How many days in the next 101 days will EXACTLY 2 chickens be laying an egg?

Answer 1

It sounds as if you need to find a good calendar with big blocks and three pens of different colors.

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Answer 2

First, you have to find the least common multiple of the number of days between eggs (2,3,4) to get 30. Then, you make a list of numbers 1-30:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30