Use signed numbers to solve.

A helicopter descended 1200 feet, rose 800 feet, and then descended 450 feet.

What was the net gain or loss in altitude?

A. lost 2450 ft

B. lost 850 ft

C. gained 850 ft

D. gained 2450 ft

Let us first concentrate on the information's already provided.

First case

The helicopter descended 1200 feet, so = - 1200

Second case

The helicopter rose 800 feet, so = 800

Then

The position at which the helicopter is now = - 1200 + 800

= - 450 feet

Third case

The helicopter again feel by 450 feet = - 450

Then

Position of helicopter = - 400 - 450

= - 850

From the above deduction, we can say that the helicopter lost 850 feet. The correct option among all the options that are given in the question is option "B".

We are given the heights and the directions of the displacements of the helicopter. We assign going up or gaining of height as positive and going down or losing as negative. In this case, - 1200 + 800 - 450 = - 850 feet. Answer is B