Growing and Shrinking

Select all sequences that could be geometric.

• C. 1, 3, 5, 7, ...

• E. 1,000, 200, 40, 8, ...

• D. 1/2, 2, 8, 32, ...

• B. 1/3, 1, 3, 9, ...

• A. 2, 4, 7, 11, ...

A blogger had 400 subscribers to her blog in January. The number of subscribers has grown by a factor of 1.5 every month since then. Choose the correct sequence to represent the number of subscribers in the 3 months that followed.

• 400,200, 100, 50

• 400, 600, 900, 1,350

• 400, 800, 1,200, 2400

• 400,500,600, 800

Tyler says that the sequence 1, 1, 1,... of repeating 1s is not exponential because it does not change. Do you agree with Tyler?

• Yes, I agree with Tyler.

• No, I do not agree with Tyler.

In 2000, an invasive plant species covered 0.2% of an island. For the 5 years that followed, the area covered by the plant tripled every year. A student said, "That means that about half of the island's area was covered by the plant in 2005!"   Do you agree with his statement?

• Yes, I agree with his statement.

• No, I do not agree with his statement.

A square picture with side length 30 cm is scaled by 60% on a photocopier. The copy is then scaled by 60% again. What is the side length of the second copy of the picture?

• 10.8 cm

• 12.6 cm

• 14.4 cm

• 16.2 cm

A square picture with side length 30 cm is scaled by 60% on a photocopier. What is the side length of the picture after it has been successively scaled by 60% 4 times?

• 10.8 cm

• 5.4 cm

• 3.9 cm

• 1.9 cm

A geometric sequence g starts 5, 15, . . . . How would you calculate the value of the 50th term?

• Add 10 to the first term and multiply by 50.

• Multiply the first term by 50.

• Use the formula for the sum of a geometric sequence.