Math Problem Statement

Suppose a stock drops in value by 40% one week, then increases in value the next week by 75%. Is the value higher or lower than where it started? The value of the stock is than where it started. If the value of the stock started at $100, then what is it worth now?

Solution

Let's break down the problem:

  1. Initial drop of 40%:

    • If the stock starts at $100 and drops by 40%, it loses 40% of its value.
    • The loss is:
      40% of 100=0.40×100=4040\% \text{ of } 100 = 0.40 \times 100 = 40
    • After the drop, the stock is worth: 10040=60100 - 40 = 60
  2. Subsequent increase of 75%:

    • After the drop, the stock is now worth $60.
    • A 75% increase on $60 is: 75% of 60=0.75×60=4575\% \text{ of } 60 = 0.75 \times 60 = 45
    • After the increase, the stock is now worth: 60+45=10560 + 45 = 105

Thus, the stock's value after these changes is $105, which is higher than where it started.

Final Answer:

  • The value of the stock is higher than where it started.
  • If the stock started at $100, it is now worth $105.

Would you like further details or clarifications on any part of this?

Here are 5 follow-up questions related to this topic:

  1. What happens if a stock drops by 50% and then increases by 50%? Will the value be the same?
  2. How does the order of percentage changes affect the final value of a stock?
  3. What is the formula for calculating percentage change over multiple periods?
  4. How do you calculate the total percentage change from successive increases and decreases?
  5. If a stock increases by 100% after dropping 50%, what will be its final value?

Tip: When a percentage decrease is followed by a percentage increase, the increase is always calculated on a smaller base, making it harder to fully recover from large drops.

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Math Problem Analysis

Mathematical Concepts

Percentage Decrease
Percentage Increase
Successive Percentage Change

Formulas

Decrease by percentage: New Value = Initial Value - (Percentage × Initial Value)
Increase by percentage: New Value = Initial Value + (Percentage × Initial Value)

Theorems

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Suitable Grade Level

Grades 6-8