25 - 21 = 4 questions of his history incorrectly ;
4 / 25 = 0.16 represents the fraction of problems he answered incorrectly ;
Answer:

Step-by-step explanation:
Given
-- initial

Required
The exponential equation
The exponential equation is

Where

We used minus, because the rate decreases..
So, we have:



So:


Hence:

Answer:
Step-by-step explanation:
12. To find the carpet needed. Find the area :
The figure is combination of semi circle and a rectangle.
So Area = Area of semi circle + Area of rectangle

Area = 150 + 39.25 = 189.25 sq ft
13. Cost per square feet = $$9.95
Therefore cost for 189.25 square feet = 9.95 x 189.25 = $1883.04