BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

n denotes.

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 200
Joined: Thu Aug 07, 2008 5:14 pm
Thanked: 1 times

n denotes.

by ska7945 » Tue Oct 07, 2008 6:17 am
<n> denotes the product of all the positive even integers that are less than n (inclusive), then what is the biggest prime factor of <20>+<22>?


oa to follow.
let's beat GMAT.
Top
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 157
Joined: Tue Oct 07, 2008 5:47 am
Thanked: 3 times

by PussInBoots » Tue Oct 07, 2008 6:28 am
<20> + <22> = <20> * (1 + 22) = <20> * 23
23 is largest prime factor, since all of prime factors of <20> are smaller than 20


<20> = 2 * 4 * 6 * 8 * 10 * 12 * 14 * 16 * 18 * 20: prime factors 2, 3, 5, 7
<22> = <20> * 22
Top
Junior | Next Rank: 30 Posts
Posts: 10
Joined: Sat Jul 19, 2008 12:24 pm

by arthi » Tue Oct 07, 2008 7:10 am
is it 5?

whats the OA?
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 316
Joined: Mon Sep 22, 2008 12:04 am
Thanked: 36 times
Followed by:1 members

by Morgoth » Tue Oct 07, 2008 7:37 am
Largest factor would be 23

<20> + <22>

<20> = 2*4*6......*20

<22> = <20>*22

Therefore,

<20> + <22> = <20> + <20>*22 = <20> ( 1+22) = <20> * 23

Thus, 23.

Hope this helps.
Top
Post new topic Post Reply
• Page 1 of 1