Question

In the set of all integers from 4 to 81, inclusive, how many are multiples of 2 or 7 or both? Explain.
A.34
B.39
C.45
D.50
E.55

Answer 1

multiples of 2....from 4 to 81
4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78,80 = 39

or 77/2 = 38.5 rounds to 39

multiples of 7...from 4 to 81
7,14,21,28,35,42,49,56,63,70,77 = 11

or 77/7 = 11

total of 50

Answer 2

Is there a faster or simpler way to do it?