An airplane begins descending at a constant rate. After 20 seconds have passed, its altitude is 1,500 feet. After 40 seconds have passed, its altitude is 1,250 feet. Which equation relates t, the time in seconds since it started descending, to a(t), the plane’s altitude in feet?

a(t) = –12.5t + 1,750
a(t) = 12.5t + 1,250
a(t) = –12.5t + 250
a(t) = 12.5t – 250

Question

An airplane begins descending at a constant rate. After 20 seconds have passed, its altitude is 1,500 feet. After 40 seconds have passed, its altitude is 1,250 feet. Which equation relates t, the time in seconds since it started descending, to a(t), the plane’s altitude in feet?

a(t) = –12.5t + 1,750
a(t) = 12.5t + 1,250
a(t) = –12.5t + 250
a(t) = 12.5t – 250

bibby · Answer

Might be a roundabout way of doing this, but you know it's losing 250 feet ever 20 seconds.

That means every t+20, a(t) goes down 250. That means we can cancel out b and d

anonymous · Answer

Is it A ?

bibby · Answer

yep

bibby · Answer

you can confirm it by plugging in 40 and getting 1250. and 20 and getting 1500