SOLUTION: A man is able to save 50naira of his salary in a particular year. After every year he saved 20naira more the preceding year. How long does it take him to save 4370naira
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Question 1198930: A man is able to save 50naira of his salary in a particular year. After every year he saved 20naira more the preceding year. How long does it take him to save 4370naira
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A man is able to save 50naira of his salary in a particular year.
After every year he saved 20naira more the preceding year.
How long does it take him to save 4370naira
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This problem introduces an arithmetic progression with the first term a= 50
and the common difference d = 20.
Then the problem asks you to determine the number of terms such that their sum is 4370.
Use the formula for the sum of arithmetic progression
= .
In this problem, it takes the form
=
and gives you this equation
4370 = (50 + 10(n-1))*n,
Reduce the common factor of 10 in both sides and simplify step by step
437 = 5n + n^2 - n
n^2 + 4n - 437 = 0.
Solve using the quadratic formula
= = .
There are two roots, one positive and the other negative.
Naturally, you want only positive number of terms n = = = 19.
ANSWER. It will take him 19 months to get his goal.
