During 2001, a stock lost 80 percent of its value

Question

During 2001, a stock lost 80 percent of its value. During the following year, the stock's value increased by 200 percent. Which of the following is the percent change in the stock's value during those two years?

A. 60 percent decrease
B. 40 percent decrease
C. 20 percent increase
D. 60 percent increase
E. 140 percent increase

A. 60 percent decrease
B. 40 percent decrease
C. 20 percent increase
D. 60 percent increase
E. 140 percent increase

Bunuel · Answer

Let the value of the stock in 2000 be 100, then in 2001 its value would be 100*(1-80/100)=100*0.2=20 and in 2002 its value would be 20*(1+200/100)=60. Hence during those two years the value of the stock decreased from 100 to 60, so by 40%.

Answer: B.

ENAFEX · Answer

Assume initial Stock value =100
Decreased by 80% 
= 100- (80% of 100)
= 20

Increased by 200%
=20+(200% of 20)
=20+40
=60

% Change = (Change/Original)*100
Change=(100-60)=40
Original = 100

40 Percent decrease

Abhishek009 · Answer

Let value of stock initially be $ 100

Value of stock after the stock lost 80 percent of its value is 20

Value of stock after 200% increase is

\frac{(200+100)}{100} * (20)

3*20 = 60

Value of stock initially was 100 but after the change the value of stock become 60, so there is a net decrease in 40%

Hence answer is (B)

TeamGMATIFY · Answer

Let us assume the initial value in 2000 = 100x
We use 100x to remove the confusion of unitary method that may arise if we assume the value to be 100.
In the end, we can simply find x and replace in 100x to get the value.

Value in 2001 = 20x
Value in 2002 = 20x + 40x (100% = 20x, 200% = 40x)

Decrease in value from 2000 to 2002 = 100x - 60x = 40x
Hence 40% decrease. Option B

Abhishek009 · Answer

There is another method of solving this problem mechanically.

Dor subsequent Increase in decrease in % terms we can directly apply the formula -  m + n +   \frac{(m*n)}{100}  ; where  m   and   n  are the corresponding change in percentage.

Here  m  = - 80 and  n  = 200

Applying the formula  m + n +   \frac{(m*n)}{100}

-80 + 200 +   \frac{(-80*200)}{100}

120 +   -160  =  -40

So, there is a net 40% decrease

Nunuboy1994 · Answer

Pick a simple value

100(.2)= 20
20(3) =60

60-100/100= 40 percent decrease

Thus 
 "B"

bumpbot · Answer

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During 2001, a stock lost 80 percent of its value

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