A graduate student is given a starting salary of 400BD per month for a programming job. The employee has been promised a salary raise of 10% per year for the first 3 years and 20% a year for each additional year. The salary raise is based on last year's salary. How long will the employee have to wait until they have a salary of 600BD per month?

The employee will have to wait for 4 years to get the salary.

Step-by-step explanation:

Given,

The salary pr month = 400BD

10% salary will be raised for the 3 years.

To find the salary 600BD per month

For, 1st year, the salary is = 400BD

For, 2nd year, the salary will be = 400 + 400 * 10%

=440BD

For, 3rd year, the salary will be = 440 + 440 * 10%

= 484BD

For, 4th year, the salary will be = 484 + 484 * 10%

= 532.4BD

Next additional year the salary will be raised 20% per year

so, for 5th year, the salary will be = 532.4 + 532.4 * 20%

=638.88BD

Hence, in 5th year the salary will be more than 600BD per month

That means, the employee has to wait for 4 years after joining to get the salary.

4 years

Step-by-step explanation:

After 3 years:

400 (1.1³) = 532.4

n additional years

600 = 532.4 (1.2^n)

1500/1331 = 1.2^n

ln (1500/1331) = n*ln1.2

n = 0.655

5th year