Question 870203: How many integers in the set {n is in Z | 1 ≤ n ≤ 1260} are divisible by 3, 5, or 7?
Answer by richwmiller(17219)   (Show Source):
You can put this solution on YOUR website! by any of them 684
by 7 180
by 5 252
by 3 420
an = a + (n - 1)d
1260 = 3 + (t - 1)3,
1260 = 5 + (f - 1)5,
1260 = 7 + (s - 1)7
1260 = 15 + (tf - 1)15,
1260 = 21 + (fs - 1)21,
1260 = 35 + (st - 1)35
1260 = 105 + (a - 1)105
tf = 60, fs = 36, st = 84 all a=12
5 f = 252, 7 s = 180, 3 t = 420
tf +fs+fst = 60+ 36+ 84=180-12=168
3*5=15
3*7=21
5*7=35
3*5*7=105
f+s+t=852
852-684=168
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