294 algebra De mystif ieD

begins to walk, they are moving toward one another at the rate of 2 + 1.5 =

3.5 meters per second.

Let t represent the number of seconds the second boy walks.

35 770

770

35

220

.

.

t

t

t

=

=

=

The boys will meet 220 seconds, or 3 minutes 40 seconds, after the second

boy starts walking.

A plane leaves City A toward City B at 9:10, flying at 200 mph. Another

plane leaves City B towards City A at 9:19, flying at 180 mph. If the cities are

790 miles apart, when will the planes pass each other?

In 9 minutes the first plane has flown (^200) () 609 = 30 miles, so when the
second plane takes off, there are 790 – 30 = 760 miles between them. The
planes are traveling toward each other at 200 + 180 = 380 mph. Let t rep-
resent the number of hours the second plane flies.
380 760
760
380
2
t
t
t

=

Two hours after the second plane has left the planes will pass each other;
that is, at 11:19 the planes will pass each other.
PRACTICE

1. Two joggers start jogging on a trail. One jogger heads north at the rate
   of 7 mph. Eight minutes later, the other jogger begins at the same point
   and heads south at the rate of 9 mph. When will they be 2 miles apart?


2. Two boats head toward each other from opposite ends of a lake, which
   is 6 miles wide. One boat left at 2:05 going 12 mph. The other boat left
   at 2:09 at a rate of 14 mph. What time will they meet?


3. The Smiths leave the Tulsa city limits, heading toward Dallas, at 6:05
   driving 55 mph. The Hewitts leave Dallas and drive to Tulsa at 6:17, driv-
   ing 65 mph. If Dallas and Tulsa are 257 miles apart, when will they pass
   each other?

PRACTICE

1. Two joggers start jogging on a trail. One jogger heads north at the rate