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

Redeem

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.

★★★★★5.0559 reviews
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
Live EA class + 6 months of EA OnDemand
  • Expert-led weekly online sessions
  • EA Masterclass access between classes
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

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

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

Difficult Math Question #21 - Probability

Expert replies
by 800guy » Tue Sep 26, 2006 5:55 pm
OA coming after some people respond...

Each of the integers from 0 to 9, inclusive, is written on a separate slip of blank paper and the ten slips are dropped into a hat. If the slips are then drawn one at a time without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10?
3
4
5
6
7
Join the discussion
Source: — Problem Solving |

by gamemaster » Tue Sep 26, 2006 11:35 pm
My solution:

we have:

1 9
2 8
3 7
4 6

and also 0 and 5

so if we choose just one half of a pair (4 numbers for example 1,2,3,4) and 0 and 5, then only on the 7th number we'll succseed

the answer will be 7 also if we look for combination of more than 2 numbers to sum up to 10, because we can choose: 9,8,7,6,5,0 first

so: E
Join the discussion

OA

by 800guy » Tue Oct 03, 2006 9:58 pm
OA:

ok consider this

0 + 1+ 2 + 3 + 4 +5 +6..Stop --> Don’t go further. Why? Here’s why.
At the worst the order given above is how u could pick the out the slips. Until u add the slip with no. 6 on it, no two slips before that add up to 10 (which is what the Q wants)

the best u can approach is a sum of 9 (slip no. 5 + slip no. 4)

but as soon as u add slip 6. Voila u get your first sum of 10 from two slips and that is indeed the answer = 7 draws
Join the discussion

by rahulg83 » Tue Jun 30, 2009 10:52 am
I really don't understand what this question is asking for?
We can simply take out 2 chits numbered 1 and 9, and get the sum 10..there could be a lot of ways to get this 2 and 8, 3 and 7..so on..
can someone help me understand the language of this question?
Join the discussion

by kaulnikhil » Tue Jun 30, 2009 1:30 pm
what question is indeed asking is that whenever you pick a new chit the sum of other chits that you have taken out and this new chit must be 10. now if we go by ur case we take out 1. the next chict we can take out any other no except1 . So u cant guarantee that the sum will be 10.
Now consider this u take out 0 ,1, 2,3,4 ,5
now whenever u take out a new chict irrespective of the no u take out sum will be 10 ..
so in all u need 7 turns
Join the discussion