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by guerrero » Mon May 13, 2013 9:38 am
A lighting store is stocked with 410 fixtures. Some of the fixtures are floor lamps and the rest are table lamps. If 5% of the floor lamps and 30% of the table lamps are imported, what is the smallest possible number of imported lamps stocked at the store?

A. 3
B. 10
C. 13
D. 20
E. 23

any easy approach ?



E
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Source: — Problem Solving |

by Brent@GMATPrepNow » Mon May 13, 2013 9:56 am
guerrero wrote:A lighting store is stocked with 410 fixtures. Some of the fixtures are floor lamps and the rest are table lamps. If 5% of the floor lamps and 30% of the table lamps are imported, what is the smallest possible number of imported lamps stocked at the store?

A. 3
B. 10
C. 13
D. 20
E. 23

any easy approach ?



E
Notice that a greater proportion of the table lamps are imported (30%).
So, to MINIMIZE the number of imported lamps, we must MINIMIZE the number of table lamps.

If 30% of the table lamps are imported, then the number of table lamps must be a multiple of 10 (since 30% = 3/10). In other words, 3 out of every 10 table lamps is imported.
For example, there cannot be 8 table lamps since 30% of 8 is not a whole number.

Likewise, the number of floor lamps must be a multiple of 20 (since 5% = 1/20).

Now that we know the number of table lamps must be a multiple of 10, and the number of floor lamps must be a multiple of 20, let's try to MINIMIZE the number of table lamps.

The smallest possible number table lamps is 10, in which case there are 400 floor lamps.
- Of the 10 table lamps, 30% are imported (3 imported)
- Of the 400 table lamps, 5% are imported (20 imported)

Total number of imported lamps = [spoiler]3 + 20 = 23 = E[/spoiler]

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Atekihcan » Mon May 13, 2013 10:00 am
Let us assume the number of imported lamps, floor lamps, and table lamps are I, f, and t, respectively. So, f = (410 - t)

Now, I = 5% of f + 30% of t = 5f/100 + 30t/100 = f/20 + 3t/10 = (410 - t)/20 + 3t/10 = [(410 - t) + 6t]/20 = (410 + 5t)/20 = (82 + t)/4 = 20.5 + (t/4) > 20

Only possible correct answer is option [spoiler]E : 23[/spoiler]
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