Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions

Lights set

Expert replies
by jessicamuniz » Sun Oct 26, 2008 8:55 am
Here is another one (at last but not ar least)...

Three utility lights are set on timers. The first flashes every 15 seconds, the second flashes every 17 seconds, and the third flashes every 20 seconds. If, at given moment, the three lights flashs at exactly the same time, how many seconds will elpase before the next such ocurrance=
a. 30
b. 255
c. 510
d. 1,020
e. 5,100

Thanksin advance
Join the discussion
Source: — Problem Solving |

by vishubn » Sun Oct 26, 2008 9:02 am
is the answer 1020 !!

I mean LCM of 15,17,20 is 1020 seconds !

i.e.

5*3*4*17=1020

so it will take 1020 seconds for such occurance

vishu

OA??
Join the discussion

by rohangupta83 » Sun Oct 26, 2008 9:21 am
it should be 1020

15,17 and 20 are all factors of 1020

imo D
Join the discussion