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Stocks

by jain2016 » Wed Mar 23, 2016 11:50 am
Certain stocks in January were 10% less than they were in February 20% greater than they were in March. What was the percentage decrease in the stocks from February to March?

A) 5%

B) 10%

C) 20%

D) 25%

E) 50%

OAD

Hi Experts ,

Please explain.

Many thanks in advance.

SJ
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by GMATGuruNY » Wed Mar 23, 2016 12:07 pm
Certain stocks in January were 10% less than they were in February and 20% greater than they were in March. What was the percentage decrease in the stocks from February to March?

A. 5%
B. 10%
C. 20%
D. 25%
E. 50%
Certain stocks in January were 10% less than they were in February.
J/F = 9/10.

Certain stocks in January were 20% greater than they were in March.
J/M = 12/10.

What was the percentage decrease in the stocks from February to March?
Ratios can be MULTIPLIED:
F/M = F/J * J/M
In this equation, the values in red CANCEL OUT.

Substituting F/J = 10/9 and J/M = 12/10 into F/M = F/J * J/M, we get:
F/M = 10/9 * 12/10 = 4/3.

Percent decrease from F=4 to M=3:
Difference/Original * 100 = (4-3)/4 * 100 = 25%.

The correct answer is D.
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by GMATGuruNY » Wed Mar 23, 2016 12:26 pm
Certain stocks in January were 10% less than they were in February and 20% greater than they were in March. What was the percentage decrease in the stocks from February to March?

A. 5%
B. 10%
C. 20%
D. 25%
E. 50%
Alternate approach:

Let F = 100.
Since the stocks were 10% less in January, J = 100 - (10% of 100) = 100-10 = 90.

We can PLUG IN THE ANSWERS, which represent the percent decrease from February to March.
When the correct answer choice is plugged in, J=90 will be 20% greater than the value of M.

Answer choice D: 25
Here, the percent decrease from F=100 to M is 25%:
M = 100 - (25% of 100) = 100-25 = 75.

M increased by 20% = 75 + (20% of 75) = 75+15 = 90, which is the value of J.
Success!

The correct answer is D.
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by Shazi1711 » Thu Mar 24, 2016 5:34 am
jain2016 wrote:Certain stocks in January were 10% less than they were in February 20% greater than they were in March. What was the percentage decrease in the stocks from February to March?

A) 5%

B) 10%

C) 20%

D) 25%

E) 50%

OAD

Hi Experts ,

Please explain.

Many thanks in advance.

SJ
I would approach the same way as Mitch did above.

Let Price in Feb = 100
Jan = 10% less than Feb therefore = 90

Let price for March = x
Therefore 1.2x = 90 (because price for Jan is 20% greater than that in March)
x = 75
Therefore the three prices are as follows :

Feb = 100
Jan = 90
March = 75

% decrease from Feb to March : 100-75 = 25 (Here you don't need to apply the %change formula as the base value (i.e. Feb) is 100)

Answer D
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