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How to Calculate Quantity Demanded When Price Is Given?

Published in Quantity Demanded 3 mins read

To calculate quantity demanded when the price is known, you typically use a specific demand equation, which models the relationship between price and the quantity consumers are willing to buy.

Calculating Quantity Demanded Using the Demand Equation

To determine the quantity demanded (Qd) for a good or service when its price (P) is known, one typically employs a specific demand equation. This equation quantifies the relationship between price and the amount consumers are willing to purchase.

The Fundamental Formula

The core formula for this calculation is:

Qd = a + b(P)

Understanding Each Component

Here's a breakdown of the variables in this equation:

  • Qd: Represents the Quantity Demanded, which is the total amount of a product or service consumers are willing and able to buy at a particular price point.
  • a: This is the x-axis intercept. It signifies the quantity demanded if the price of the good were zero.
  • b: This term stands for the slope of the demand curve. It indicates how much the quantity demanded changes for every one-unit change in price.
  • P: This is the Price of the good or service for which you are calculating the demand.
Variable Description
Qd Quantity Demanded
a The x-axis intercept (quantity demanded when price is zero)
b The slope of the demand curve, showing change in Qd per unit change in P
P The specific price of the good

The Relationship Between Price and Quantity Demanded

In this context, quantity demanded has a direct relationship with price. This means that as the price of a good increases, the quantity demanded for that good also increases, assuming a positive slope for 'b'.

Practical Example

Let's illustrate how to use this formula with a hypothetical scenario.

Scenario:
Imagine a company sells custom-designed T-shirts, and their demand equation has been determined to be:

Qd = 100 + 2(P)

Where:

  • a (x-axis intercept) = 100 T-shirts
  • b (slope of the demand curve) = 2
  • P = Price of one T-shirt

Problem: How many T-shirts will be demanded if the price (P) is set at $15 per T-shirt?

Solution Steps:

  1. Identify the given price: P = $15
  2. Substitute the price into the demand equation:
    Qd = 100 + 2(15)
  3. Perform the multiplication:
    Qd = 100 + 30
  4. Perform the addition:
    Qd = 130

Therefore, at a price of $15 per T-shirt, the quantity demanded would be 130 T-shirts.

Understanding the demand equation is crucial for businesses to forecast sales, set prices strategically, and manage inventory effectively based on consumer willingness to purchase at various price points. For more information on demand concepts, you can explore resources on demand curves.