You are paying for your niece's education every month; contribution decreasing monthly at a constant rate. if your 20th contribution (after 19 months) was $483 and 43rd contribution was $345, what was your first contribution?

The first contribution was 637.77

Step-by-step explanation:

Geometric Sequences

It a type sequence in which each term is computed as the previous term by a constant number. The general expression for a geometric sequence is

If we know two terms of the sequence, say n=k and n=p, then

and

We can determine the values of and r, by manipulating both equations

We know that

Dividing both expressions, we have

Solving for r

Now we use

to compute

step-by-step explanation:

you divide the denominator by the numerator on both sides and if the quotients are equal then the fractions are equivalent