Akriti Posted November 14, 2010 Report Share Posted November 14, 2010 The combined age of reena and seena is 44 yrs and reena is twice as old as seena was when reena was half as old as seena will be when seena is three times as old as reena was when reena was three times as old as seena. How old is reena? Quote Link to comment Share on other sites More sharing options...
0 araver Posted November 14, 2010 Report Share Posted November 14, 2010 (edited) After six months, Seena will be 17 and Reena will be 28. Or a more direct answer: Reena is 27 1/2 years old now. (1) r+s=44 (2) r=2*s1 (3) r1=s2/2 (4) s2=3*r3 (5) r3=3*s3 ------- r>s (from (5)) Let t=r-s=r1-s1=r2-s2=r3-s3>0. Then (6) t=2*s3 (from (5)) r= (from (2)) =2*(r1-t)= (from (3)) =2*(s2/2-t) = (from (4)) =3*r3-2*t = =3*s3+3*t-2*t = (from (6)) =3*t/2+t=5/2*t s=r-t= 5/2*t-t=3*t/2 44=r+s=5/2*t+3*t/2=4*t Therefore t=11, s=(44-11)/2=16.5, r = s+t = 27.5 Edited November 14, 2010 by araver Quote Link to comment Share on other sites More sharing options...
0 wolfgang Posted November 14, 2010 Report Share Posted November 14, 2010 Hmmmmmm....I am totally confused!! Quote Link to comment Share on other sites More sharing options...
0 Akriti Posted November 14, 2010 Author Report Share Posted November 14, 2010 great job ,but actually I couldn't understand it. Quote Link to comment Share on other sites More sharing options...
0 araver Posted November 14, 2010 Report Share Posted November 14, 2010 Hmmmmmm....I am totally confused!! great job ,but actually I couldn't understand it. Sorry, I was in a hurry Let r=age of Reena now and s = age of Seena now. Then from the first statement we get: (1) r+s=44 Reading further: "...Reena is twice as old as Seena was ..." sometime ago - let's call it Time 1. Let s1 and r1 be the ages of Seena and Reena in time 1. Then this statement means: (2) r=2*s1 Reading further: "... as seena was when reena was half as old as seena will be when ... " - sometime in the future - let's call it Time 2. Let s2 and r2 be the ages of Seena and Reena in time 2. Then this statement means: (3) r1=s2/2 Reading further: "...when seena is three times as old as reena was... " sometime ago - Time 3. Let s2 and r2 be the ages of Seena and Reena in time 3. Then this statement means: (4) s2=3*r3 Reading further: "...when reena was three times as old as seena. " still in Time 3, so: (5) r3=3*s3 From (5) we get that Reena is older than Seena. But the age difference between Reena and Seena is constant so: Let t=r-s=r1-s1=r2-s2=r3-s3>0 Then replacing r3 in (5) we get: (6) t=2*s3 And now we use all these relations backwards to see how old is Reena now (in terms of t). Each time a previous statement is used it is marked. r= (from (2)) = 2*(r1-t) = (from (3)) = 2*(s2/2-t) = (from (4)) = 3*r3-2*t = (def. of t) = 3*s3+3*t-2*t = (from (6)) = 3*t/2+t = 5*t/2 Then s = r-t = 5/2*t - t= 3*t/2 Replacing in (1): 44 = r+s = 5*t/2 + 3*t/2 =4*t Therefore t=11, s=(44-11)/2=16.5, r = s+t = 27.5 Quote Link to comment Share on other sites More sharing options...
0 Akriti Posted November 15, 2010 Author Report Share Posted November 15, 2010 Thanks a lot Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 15, 2010 Report Share Posted November 15, 2010 Omg i wonder who makes these age riddles up.It would be realy easier to track down Reena and Seena and ask them their names! Quote Link to comment Share on other sites More sharing options...
Question
Akriti
The combined age of reena and seena is 44 yrs and reena is twice as old as seena was when reena was half as old as seena will be when seena is three times as old as reena was when reena was three times as old as seena. How old is reena?
Link to comment
Share on other sites
6 answers to this question
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.