Freddy has a piece of string that is 20 inches. . .

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Vincen: Legendary Member; Posts: 2898; Joined: Thu Sep 07, 2017 2:49 pm; Thanked: 6 times; Followed by:5 members

Freddy has a piece of string that is 20 inches. . .

by Vincen » Fri Sep 15, 2017 7:26 pm

Freddy has a piece of string that is 20 inches long. He wants to use the string as the perimeter of a rectangle. What is the greatest area that rectangle could have?

A) 5
B) 10
C) 20
D) 25
E) 40

The Official Answer is D.

I couldn't do the calculus to solve it. Please, help me.

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Source: Beat The GMAT — Problem Solving | Fri Sep 15, 2017 7:26 pm

GMAT/MBA Expert

[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pm; Location: Palo Alto, CA; Thanked: 2867 times; Followed by:511 members; GMAT Score:800

by [email protected] » Sat Sep 16, 2017 10:52 am

Hi Vincen,

We're asked to use a 20 inch string to form the perimeter of a rectangle. We're asked for the LARGEST possible rectangular area that could be created. This question is built around a relatively rare concept (while you might see it on Test Day, it would likely be just once). In simple terms, when dealing with a 'fixed' total length as described in the prompt, the largest area will be created when you form a SQUARE.

For example, with a 20 inch string, you could form the following rectangles:
A 1x9 rectangle with an area of 9
A 2x8 rectangle with an area of 16
A 3x7 rectangle with an area of 22
A 4x6 rectangle with an area of 24
A 5x5 rectangle with an area of 25

There's no other possible rectangle that will lead to an area that is larger than 25.

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

Re: Freddy has a piece of string that is 20 inches. . .

by Scott@TargetTestPrep » Sun Feb 02, 2020 1:53 pm

Vincen wrote: ↑
Fri Sep 15, 2017 7:26 pm
Freddy has a piece of string that is 20 inches long. He wants to use the string as the perimeter of a rectangle. What is the greatest area that rectangle could have?

A) 5
B) 10
C) 20
D) 25
E) 40

The Official Answer is D.

I couldn't do the calculus to solve it. Please, help me.