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ashish: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Tue Dec 23, 2014 2:39 am

by ashish » Sun Jan 04, 2015 8:49 am

Each M type memory unit will increase the base memory capacityof a certain computer by 3 MB. what is the base memory in MB of computer?

I 2 M type memory units will increase the base memory by 300 %.
II The memory capacity of computer after 2 Mtype units are added to base memory capacity is 1.6 times the memory capacity of computer after the M type memory unit is added to the base memory capacity.

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Source: Beat The GMAT — Data Sufficiency | Sun Jan 04, 2015 8:49 am

MartyMurray: Legendary Member; Posts: 2135; Joined: Mon Feb 03, 2014 9:26 amFollowed by: 140 members; Location: https://martymurraycoaching.com/; Thanked: 955 times; GMAT Score:800

by MartyMurray » Sun Jan 04, 2015 9:29 am

ashish wrote:Each M type memory unit will increase the base memory capacityof a certain computer by 3 MB. what is the base memory in MB of computer?

I 2 M type memory units will increase the base memory by 300 %.
II The memory capacity of computer after 2 Mtype units are added to base memory capacity is 1.6 times the memory capacity of computer after the M type memory unit is added to the base memory capacity.

Ok, know that each unit increases memory by 3. So it looks as if the question is can we somehow use this to get to the base memory.

Statement 1 says that adding two units increases memory by 300% over base memory, b. We know that two units add up to 6 MB. So if 6 is 300% of b, then we can figure out b. We don't need to calculate b, just to know that we can.

Sufficient

Statement 2 says that b + 2 units = 1.6(b + 1 unit). We know the units each add 3 MB, so we can use that in the equation to get b + 6 = 1.6(b + 3) So b + 6 = 1.6b + 4.8 and 1.2 = .6b This can obviously be solved for b. No need to go further.

Sufficient

Choose D.

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sun Jan 04, 2015 11:00 am

For statement 2, I believe you need to change "the" to "ONE".

ashish wrote:Each M-type memory unit will increase the base memory capacity of a certain computer by 3 MB. What is the base memory in MB of computer?

1) 2 M-type memory units will increase the base memory by 300 %.
2) The memory capacity of computer after 2 M-type units are added to base memory capacity is 1.6 times the memory capacity of computer after ONE M-type memory unit is added to the base memory capacity.

Target question: What is the base memory in MB of computer?

Given: Each M-type memory unit will increase the base memory capacity of a certain computer by 3 MB.

Statement 1: 2 M-type memory units will increase the base memory by 300 %.
From the given information, we know that 2 M-type memory units will increase the base memory by a total of 6 MB.
Let x = the BASE memory (in MB) of the computer.
So, with the 2 M-type memory units, the NEW memory is x + 6 MB
Represents a 300% increase.

FORMULA: Percent increase = 100(new - old)/old
So, we can write: 300 = 100(x + 6 - x)/(x)
Simplify: 300 = 600/x
So, x = 2
In other words, the BASE memory of the computer is 2 MB.
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: The memory capacity of computer after 2 M-type units are added to base memory capacity is 1.6 times the memory capacity of computer after ONE M-type memory unit is added to the base memory capacity.
Let x = the BASE memory (in MB) of the computer.
So, when TWO M-type memory units are added, the NEW memory is x + 6 MB
When ONE M-type memory unit is added, the NEW memory is x + 3 MB

We're told that x + 6 is 1.6 TIMES x + 3
So, we can write: x + 6 = 1.6(x + 3)
At this point, we should recognize that we COULD solve this equation for x, which means we COULD find the the BASE memory of the computer.
Since we COULD answer the target question with certainty, statement 2 is SUFFICIENT

Answer = D

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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utkalnayak: Senior | Next Rank: 100 Posts; Posts: 53; Joined: Thu Dec 25, 2014 2:23 pm; Thanked: 1 times

by utkalnayak » Sun Jan 04, 2015 5:14 pm

ashish wrote:Each M type memory unit will increase the base memory capacityof a certain computer by 3 MB. what is the base memory in MB of computer?

I 2 M type memory units will increase the base memory by 300 %.
II The memory capacity of computer after 2 Mtype units are added to base memory capacity is 1.6 times the memory capacity of computer after the M type memory unit is added to the base memory capacity.

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Matt@VeritasPrep: GMAT Instructor; Posts: 2630; Joined: Wed Sep 12, 2012 3:32 pmFollowed by: 119 members; Location: East Bay all the way; Thanked: 625 times; GMAT Score:780

by Matt@VeritasPrep » Mon Jan 05, 2015 11:18 am

Let's say the base capacity is b.

S1 gives us the equation b + 2*3 = b + (300% of b), which is really b + 6 = 4b, or b = 2. SUFFICIENT

S2 gives us the equation b + 2*3 = 1.6 * (b + 3), which is really b + 6 = 1.6b + 4.8, or b = 2. SUFFICIENT

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