Question

E.

DATE
Topic
PERI
mountain road is 5 miles long and gains elevation at a constant rate.
fter 2 miles, the elevation is 5,500 feet above sea level.
Fter 4 miles, the elevation is 6,200 feet above sea level. (Lesson 3-6)
Find the elevation of the road at the point where the road begins.

Answer 1

Explanation:

this is about the overall slope of the mountain road.

remember, the slope is (y change / x change). in this case it is elevation change / distance change.

getting from 2 to 4 miles the changes are

distance changes by +2

elevation changes by + 700 (from 5500 to 6200).

the slope is +700/+2 = 350/1 = 350.

the road begins at distance = 0.

the elevation of the begin of the road = x.

so going from 2 miles down again to 0 the changes are

distance changes by -2 (from 2 to 0)

elevation changes by x - 5500 (from 5500 to x).

the slope there must be the same as the slope further up (as it is said it has a constant rate) :

(x - 5500)/-2 = 700/2

(5500 - x)/2 = 700/2

5500 - x = 700

x = 5500 - 700 = 4,800 ft

the road started at an elevation of 4,800 ft above sea level.