A man saves N 100.00 in his first year of work and each year saves...

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?

The correct answer is: C

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

There is an explanation video available .