How many positive integers less than 1000 are multiples of 5 but NOT of 4 or 7?
a)114
b)121
c)122
d)129
e)136
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wingsoffire
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rajanjindal27
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129.
20 multiples of 5 in each 100 number set (5,10,15...90,95,100)
= 20(10)
subtract 5 from each set that are multiples of 4 (20,40,60,80,100) <-- takes care of 1000 since its "less than 1000"
so now its 15(10).
subtract 21 for all the multiples of 7 (manually crunched it, didn't double count the multiples of 4 already subtracted).
=150 - 21 = 129
Took about 3 minutes with the manual number crunching of multiples of 7 that didnt double dip the fours.
20 multiples of 5 in each 100 number set (5,10,15...90,95,100)
= 20(10)
subtract 5 from each set that are multiples of 4 (20,40,60,80,100) <-- takes care of 1000 since its "less than 1000"
so now its 15(10).
subtract 21 for all the multiples of 7 (manually crunched it, didn't double count the multiples of 4 already subtracted).
=150 - 21 = 129
Took about 3 minutes with the manual number crunching of multiples of 7 that didnt double dip the fours.
