The table shows the number of texts Terri received in certain periods of time.
Time (min) 1 2 3 4
Number of Texts 3 6 9 12
1. Is the relationship between number of texts and time a proportional
relationship?
2. For each column of the table, write a fraction and find k, the constant
of proportionality.

3. Express this relationship in the form of an equation:
4. What is the rate of change?
Write the equation for each table. Let x be time or weight.
5. 6.

LESSON
4-2
1. Time (h) 1 2 3 4
Distance (mi) 35 70 105 140

2. Weight (lb) 3 4 5 6
Cost ($) 21 28 35 42

Submarines control how much they float or sink in the ocean by changing the volume of air and water contained in large ballast tanks. when the tanks are completely full of water, the submarine increases its overall mass and sinks down to the bottom. when the tanks are completely full of air, the submarine reduces its overall mass and floats to the surface. depending on the density of the seawater surrounding the submarine, it will pump seawater in or out of the tanks in order to achieve the same overall density as the sea water and float neutrally in the water. the volume of the submarine never changes. when the tanks are completely full of water, a submarine with a volume of 7.8\times10^3\text{ m}^37.8×10 3 m 3 7, point, 8, times, 10, start superscript, 3, end superscript, space, m, start superscript, 3, end superscript has a total mass of 8\times10^6\text{ kg}8×10 6 kg8, times, 10, start superscript, 6, end superscript, space, k, g. the density of the seawater is 10^3\text{ kg/m}^310 3 kg/m 3 10, start superscript, 3, end superscript, space, k, g, slash, m, start superscript, 3, end superscript. to make that submarine float neutrally, and neither float nor sink in the ocean, what volume of water does that submarine need to subtract from its tanks?