Question

The stock market has been really volatile the past two days. Yesterday, it rose by x% and today it fell by x%, resulting in an overall loss of 64%. What is x?

Answer 1

x = 80%

Explanation:

Let the initial value be y

it rose by x%

That will be;

y + x/100 * y

= y + xy/100

Now, it fell by x%

That would give;

(y + xy/100)- (x/100(y + xy/100)) to give a total fallout of = y-0.64y = 0.36y

y + xy/100 - xy/100 - x^2y/10,000 = 0.36y

y - x^2y/10,000 = 0.36y

Cut out all y

1-x^2/10,000 = 0.36

Multiply through by 10,000

10,000 - x^2 = 3600

x^2 = 10,000-3600

x^2 = 6400

x = √6400

x = 80