A man saves N 100.00 in his first year of work and each year saves N 20.00 more in the preceding year. In how many years will he save N 5800.00?
A
58 years
B
100 years.
C
20 years
D
29 years
Verified Correct Answer: C.
Step-by-Step Mathematical Solution
a = N 100.00, d = N 20.00, Un = N 5800.00, n = ?
Un = \(\frac{n}{2}\)(2a + (n - 1)d)
5800 = \(\frac{n}{2}\)( 2 x 100 + ( 20n - 20)
11600 = 200n + 20n\(^2\) - 20n
20n\(^2\) + 180n - 11600 = 0
divide through by 20
n\(^2\) + 9n - 580 = 0
solve using the quadratic formula
n = 20 0r - 29
n = 20 years
Years cannot be calculated in - Ve
Source: Myschool Past Questions Archive (Record #70086)