Answer:
Ohn has paid $5730 in first 20 installments
Step-by-step explanation:
As per the question Ohn payed the first installment =$100
Next month Ohn payed the installment = 1.1×$100
Similarly subsequent installment =1.1×1.1×$100
So we can write first 20 installments as
⇒100+100×1.1+100×1.1²+100×1.1³.........+100×
And we know in geometric series
1+x²+x³+........... = (1-
)÷(1-x)
Therefore sum of first 20 installments will be
⇒100(1+1.1²+1.1³............ =(1-
)÷(1-1.1)
= 100(1-6.73)÷(-.1)
=100×5.73÷.1
= $5730
So Ohn has paid $5730