Question

Mr. and Mrs. Miller both get in their cars and begin to drive at the same time. Mr. Miller is 280 mi from their house and drives directly home at a constant rate of 40 mph. Mrs. Miller is at their house and drives away from the house at a constant rate of 30 mph. Let d represent distance from home, and let t represent time in hours. Which system models this situation? A. d = 280 + 40t d = 30t. B. d = 280 − 30t d = 40t. C. d = 280 − 40t d = 30t. D. d = 280 − 40t d = 280 + 30t

Answer 1

Given:
Mr. Miller = 280 miles from the house ; rate of 40 mph
Mrs. Miller = rate of 40 mph ; find the distance.

Speed = distance / time

time = distance / speed
time = 280 mi / 40 mph = 280 miles * 1h/40mi = 280 h/40 = 7 hours

distance = speed * time
distance = 30 mph * 7 hours = 210 miles

Correct answer would be:
A) d = 280 + 40t for Mr. Miller
d = 30t for Mrs. Miller