In the expression, surface area `=4pir^2` the factor 4 is an exact number. How many number of significant figures are there in the factor 4?

Explanation

To determine the number of significant figures in the factor 4 from the expression for surface area \( A = 4\pi r^2 \), we can follow these steps:

### Step 1: Understand the Concept of Exact Numbers
An exact number is a number that has no uncertainty associated with it. Examples of exact numbers include counts of objects (like 4 apples) or defined quantities (like 1 meter = 100 centimeters).

### Step 2: Identify the Factor in Question
In the expression for surface area, the factor 4 is a coefficient that is used to calculate the surface area of a sphere.

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