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03 Nov 2014, 09:31
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
42% (02:30) correct
58%
(02:42)
wrong
based on 529
sessions
History
Date
Time
Result
Not Attempted Yet
Tough and Tricky questions: Word Problems.
Bobby and his younger brother Johnny have the same birthday. Johnny's age now is the same as Bobby's age was when Johnny was half as old as Bobby is now. What is Bobby's age now?
(1) Bobby is currently four times as old as he was when Johnny was born.
(2) Bobby was six years old when Johnny was born.
08 Mar 2016, 21:42
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RITU700
Hi,
A real GOOD Q worth the TAG 700 level..
To do this Q, you have to UNDERSTAND what it means...
Let the ages be..
Bobby Now= B
Bobby then=b
Johnny Now=J and
Johnny then=j..
1) Johnny's age now is the same as Bobby's age was when Johnny was half as old as Bobby is now
When johnny was half as old as bobby nwo... j=B/2..
what was bobby then : b, so J=b..
now the difference in Johnny's age then and now, and bobby's age then and now should be SAME, as same years have passed for both..
therefore J-j=B-b
Solution--
1) J-j=B-b
2) J=b, and
3) j=B/2
lets get all terms in values of B or b..
so
b-B/2=B-b..
2b=3B/2..
since we have ratios of all through above ratio, we require a NUMERIC value to find answer..
Lets see the statements
(1) Bobby is currently four times as old as he was when Johnny was born.
Just gives another ratio ... no NUMERIC value
Insuff
(2) Bobby was six years old when Johnny was born.
this gives us the difference in age of two J-B=j-b=6..
now j=B/2 so j-b=B/2-b=6..
or b=B/2 + 6..
Substitute this in our Equation 2b=3B/2..
so 2(B/2 + 6)=3B/2..
B+12=3B/2
or 2B+12*2=3B..
B=24..
Suff
B..
Of course, we can do a bit of intelligent guessing,
the Q gives us a ratio..
Statement 1 gives us another Ratio
so 1 cannot be suff on its own.. eliminate A and D..
Statement 2 gives you a numeric value..
Now you have a numeric value and a ratio..
in all likelihood we should get an answer, eliminate E....
betweenB and C, for the above mentioned reason you should be inclined towards B..
atleast you have got your probability of answering correctly to 1/2 from 1/5..[/b]
+1 kudos for good Q to you and to manhattan mgmat
14 Jul 2017, 11:03
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1) INSUFFICIENT: Bobby's age at the time of Johnny's birth is the same as the difference between their ages, y - x. So statement (1) tells us that y = 4(y - x), which reduces to x = (3/4)y. This adds no more information to what we already knew! Statement (1) is insufficient.
(2) SUFFICIENT: This tells us that Bobby is 6 years older than Johnny; i.e., y = x + 6. This gives us a second equations in the two unknowns so, except in some rare cases, we should be able to solve for both x and y -- statement (2) is sufficient. Just to verify, substitute x = (3/4)y into the second equation to obtain y = (3/4)y + 6 , which implies y = 24. Bobby is currently 24 and Johnny is currently 18.
The correct answer is B, Statement (2) ALONE is sufficient to answer the question, but statement (1) alone is not.
(2) SUFFICIENT: This tells us that Bobby is 6 years older than Johnny; i.e., y = x + 6. This gives us a second equations in the two unknowns so, except in some rare cases, we should be able to solve for both x and y -- statement (2) is sufficient. Just to verify, substitute x = (3/4)y into the second equation to obtain y = (3/4)y + 6 , which implies y = 24. Bobby is currently 24 and Johnny is currently 18.
The correct answer is B, Statement (2) ALONE is sufficient to answer the question, but statement (1) alone is not.
