BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
RedeemTarget Test Prep · GMAT
Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.
with Chris Peckover, 100th-Percentile GMAT Scorer
Self-paced EA prep. Study on your schedule.
with Logan Thompson
Complete access from day one. Study on your schedule.
Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.
4 people have 1 sibling means there are 2 pairs of siblings.Jinglander wrote:In a room filled with 7 people, 4 have 1 sibling and 3 have two siblings. If two people at selected at random what is the prob that they are not siblings.
Answer is 6/21
Can someone explain.
thank you....is the way of approach is correct..what is correct OA?Rahul@gurome wrote:4 people have 1 sibling means there are 2 pairs of siblings.Jinglander wrote:In a room filled with 7 people, 4 have 1 sibling and 3 have two siblings. If two people at selected at random what is the prob that they are not siblings.
Answer is 6/21
Can someone explain.
Let A and B be the siblings, and C and D be the other pair of siblings.
Since 3 people have 2 siblings, so let E, F and G be the pair of 3 siblings.
Total no. of favorable ways of selecting 2 people from 7 people = 7C2 = 7!/(2!)(5!) = 21 ways
No. of favorable ways of selecting a sibling pair = 1 + 1 + 3 = 5 ways (We can select pairs from A-B, C-D, E-F, F-G, E-G)
Probability that they are siblings = 5/21
Probability that they not siblings = 1 - 5/21 = 16/21
New here Create free account
