Question

A large asteroid crashed into a moon of another planet causing several boulders from the moon to be propelled into space toward the planet. Astronomers were able to measure the speed of one of the projectiles.

The distance (in feet) that the projectile traveled each second, starting with the first second, was given by the arithmetic progression 19, 57, 95, 133,... Find the distance that the projectile traveled in the seventh second.

Answer 1

a. 247 ft
b. 266 ft
c. 209 ft
d. 285 ft

Answer 2

just use what you know about APs
Clearly,
a = 19
d = 38
So a7 = 19+6*38 = ____