Math

A train flies round trip at a distance of X miles each away. The velocity with the head wind is 160mph, while the velocity with tail wind is 240mph, What is the average speed for the round trip?

[HS Finance] Finance problems.

A. Find the period of deferral in each of the following deferred annuity problem.

1. Monthly payments of P1,000 for 9 years that will start 9 months from now

2. Monthly payments of P200 for 6 years that will start at the end of 10 years

3. Semi-annual payments of P12,700 for 5 years that will start 2 years from now

B. Solve the following problems completely.