Question

A bird flies across your backyard at 4.0 feet per second. How many miles can the bird travel in 2.1 hours (rounded to the nearest tenth)?
A) 2.8 mi
B) 3.2 mi
C) 5.7 mi
D) 9.7 mi

Answer 1

1 minute = 60 seconds
1 hour = 60 minutes = 60*60 seconds = 3600 seconds
1 hour = 3600 seconds

Multiply both sides by 2.1 to get
1 hour = 3600 seconds
2.1*(1 hour) = 2.1*(3600 seconds)
2.1 hours = 7560 seconds

Now use the formula below
d = r*t
where,
d = distance
r = rate or speed
t = time

In this case,
d = unknown
r = 4 ft per sec
t = 7560 seconds (equivalent to 2.1 hours)

So,
d = r*t
d = 4*7560
d = 30240
The bird can travel 30240 feet. Convert this to miles by dividing the value by 5280 (since 1 mile = 5280 feet)

30240/5280 = 5.727 roughly which rounds to 5.7

Answer: C) 5.7 miles