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# What is the sum of the first 50 common numbers between the

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Manager
Joined: 28 Feb 2003
Posts: 103
Followers: 1

Kudos [?]: 2 [0], given: 0

What is the sum of the first 50 common numbers between the [#permalink]  13 Jun 2003, 04:24
00:00

Difficulty:

5% (low)

Question Stats:

100% (04:16) correct 0% (00:00) wrong based on 1 sessions
What is the sum of the first 50 common numbers between the series 15,19,23....... and 14,19,24.........?

A) 25550
B) 24540
C) 24450
D) 25450
E) 25540
Manager
Joined: 25 May 2003
Posts: 55
Followers: 1

Kudos [?]: 3 [0], given: 0

series increasing by 4 and 5 respectively..LCM=20

therefore, they'll have common numbers every 20...so 19, 39, 59...

final number = 49x20 + 19 = 1018

therefore average = 509

so sum= 509x50= 25450

capeche??

great question btw
Manager
Joined: 28 Feb 2003
Posts: 103
Followers: 1

Kudos [?]: 2 [0], given: 0

The common numbers will also be an arithmatic series starting with 19 and with a difference of 20 (LCM of 4 and 5) between consecutive numbers....

therefore a=19
d=20
n=50

sum of arithmatic series

s = n/2(a+(n-1)*d) = 25(19+49*20) = 25450
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