This is an exponential decay problem.
Using the equation Y = a *(1-rate)^time
where Y is the future value given as 12,000 and a is the starting value given as 13,000.
The rate is also given as 5%.
The equation becomes:
12,000 = 13,000(1-0.05)^x
12,000 = 13,000(0.95)^x
Divide each side by 13000:
12000/13000 = 0.95^x/13000
12/13 = 0.95^x
Use the natural log function:
x = ln(12/13) / ln(0.95)
x = 1.56 years. ( this will equal 12,000
Round to 2 years it will be less than 12000.
40 new accounts for: 100 customer calls
10,000 new accounts for: x customer calls.
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40 : 10,000 = 100 : x
x = (100 · 10,000 ) : 40 = 25,000
Answer: 25,000 customer calls were made.
The area of the triangle should be 20. Try that out
