Problem Solving

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phoenix9801: Master | Next Rank: 500 Posts; Posts: 190; Joined: Thu Jan 14, 2010 8:29 pm; Thanked: 2 times

Problem Solving

by phoenix9801 » Sat May 26, 2012 3:42 am

Can Someone show me how to solve using plugging in numbers not in algebraically. Please be simple as possible in details. Thanks

I think the best to solve this problem in to try each answer choices, but for some reason I not sure why I am off. can some help clear wording in this problem and how to solve it using the answer choices as start?

Gerald is three times as old as his cousin Lucy and 14 years old than his parrot Polly. In 4 years Lucy will be half as old as Polly will be then. How old is Gerald?

a) 24
b) 36
c) 45
d) 54
e) 60

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Source: Beat The GMAT — Problem Solving | Sat May 26, 2012 3:42 am

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Sat May 26, 2012 4:01 am

phoenix9801 wrote:Can Someone show me how to solve using plugging in numbers not in algebraically. Please be simple as possible in details. Thanks

I think the best to solve this problem in to try each answer choices, but for some reason I not sure why I am off. can some help clear wording in this problem and how to solve it using the answer choices as start?

Gerald is three times as old as his cousin Lucy and 14 years old than his parrot Polly. In 4 years Lucy will be half as old as Polly will be then. How old is Gerald?

a) 24
b) 36
c) 45
d) 54
e) 60

Back solving Approach:

Let's start from the option E.

Let Gerald's age = 60 years.
G = 3L and G = P + 14 implies Lucy's age = 20 years and Polly's age = 46 years
After 4 years: Polly's age = 46 + 4 = 50 years and Lucy's age = 24 years, which is not one-half of Polly's age. So, this is not the correct answer.

Now consider option D:

Let Gerald's age = 54 years.
G = 3L and G = P + 14 implies Lucy's age = 18 years and Polly's age = 40 years
After 4 years: Polly's age = 40 + 4 = 44 years and Lucy's age = 18 + 4 = 22 years, which is one-half of Polly's age. So, this is the correct answer.

The correct answer is D.

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GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Sat May 26, 2012 4:02 am

Algebraic Approach:

G = 3L and G = P + 14
So, 3L = P + 14
L = (P + 14)/3
After 4 years, L + 4 = (1/2)(P + 4)
Substituting, the value of L, in L + 4 = (1/2)(P + 4),
[(P + 14)/3] + 4 = (1/2)(P + 4)
2P + 28 + 24 = 3P + 12
P = 40

So, G = 40 + 14 = 54

The correct answer is D.