Solution:
Let A be the set of numbers between 1 and 2016 divisible by 4.
Let B be the set of numbers divisible by 6.
Let C be the set of numbers divisible by 10.
We are to find ∣A∖(B∪C)∣+∣B∖(A∪C)∣+∣C∖(A∪B)∣.
First, compute the sizes of the sets:
∣A∣=⌊42016⌋=504
∣B∣=⌊62016⌋=336
∣C∣=⌊102016⌋=201
Now, intersections:
∣A∩B∣ is numbers divisible by lcm(4,6)=12:
∣A∩B∣=⌊122016⌋=168
∣A∩C∣ is numbers divisible by lcm(4,10)=20:
∣A∩C∣=⌊202016⌋=100
∣B∩C∣ is numbers divisible by lcm(6,10)=30:
∣B∩C∣=⌊302016⌋=67
∣A∩B∩C∣ is numbers divisible by lcm(4,6,10)=60:
∣A∩B∩C∣=⌊602016⌋=33
Now, for exactly one:
Numbers divisible by 4 only:
∣A∣−∣A∩B∣−∣A∩C∣+∣A∩B∩C∣=504−168−100+33=269
Numbers divisible by 6 only:
∣B∣−∣A∩B∣−∣B∩C∣+∣A∩B∩C∣=336−168−67+33=134
Numbers divisible by 10 only:
∣C∣−∣A∩C∣−∣B∩C∣+∣A∩B∩C∣=201−100−67+33=67
Total: 269+134+67=470
Answer: 470