Geometric progressions - finance?

Question

An employee begins working with a company on a salary of $20000 per annum. Her salary is to increase by 10% per year.

a) How much will she earn in the tenth year of her employment?

b) What total salary will be paid to her during the first 10 years of her employment?

Please show working.

Answer 1

(1) $20000 * ( 1.1^9 )

    1,  1.1, 1.1*1.1 ..... or

    1, X, X*X , X*X*X .....  X=1.1

(2) (1.1^10 -1 )/ (1.1-1 ) *$20000

    (1 + X + X*X +... X^9)

= ( 1 - X^10 )/ (1 - X)

= (X^10 -1 ) /( X -1 )