Two research submarines start to rise vertically toward the ocean surface. The Tri-I sub is at 4,863 feet below sea level (or –4,863 feet) and is ascending 81.1 feet per minute. The Quad-II sub is at 3,645 feet below sea level (or –3,645 feet) and is ascending 76.9 feet per minute. If the ocean surface is at 0 feet, how many minutes ( m
) must elapse for the two submarines to reach the same depth?

6.
Step 1: Choose the general equation for this situation.

rate of ascent of Quad-II sub
≤
rate of ascent of Tri-I sub

rate of ascent of Tri-I sub = rate of ascent of Quad-II sub

depth of Quad-II sub
≤
depth of Tri-I sub

depth of Quad-II sub = depth of Tri-I sub

number of minutes elapsed for Tri-I sub = number of minutes elapsed for Quad-II sub

7.
Step 3: Select the correct equation for the given situation. Then, select the solution for that equation.

m
=
290
minutes

m
=
145
minutes

-
4
,
863
+
81.1
m
=
-
3
,
645
+
76.9
m

-
4
,
863
+
76.9
m
=
-
3
,
645
+
81.1
m

m
≤
53.8
minutes

-
4
,
863
-
81.1
m
≥
-
3
,
645
+
76.9
m

m
=
53.8
minutes

4
,
863
-
76.9
m
=
3
,
645
-
81.1
m

8.
Step 2: What does the variable represent in this problem?

The variable
m
represents the depth in feet.

The variable
m
represents the distance between the two subs in feet.

The variable
m
represents the number of minutes elapsed.

The variable
m
represents the rate of ascent in feet per minute.