Question bank / Two-variable data: models and scatterplots

Math · Problem-Solving and Data AnalysisEasy
Month Number of users
1 2,000
2 3,000
3 4,500
4 6,750

The table shows the number of users of a new app at the end of each of its first 44 months. Which of the following best describes the relationship between the month and the number of users?

A

Linear, because the number of users increases by the same amount each month

B

Linear, because the number of users increases by the same percentage each month

C

Exponential, because the number of users increases by the same amount each month

D

Exponential, because the number of users increases by the same percentage each month

Show answer and explanation

Answer: D

The increases are 1,0001{,}000, 1,5001{,}500, and 2,2502{,}250, so the amount added each month isn't constant, and the relationship isn't linear. Each value is 1.51.5 times the one before it, since 3,0002,000=4,5003,000=6,7504,500=1.5\frac{3{,}000}{2{,}000} = \frac{4{,}500}{3{,}000} = \frac{6{,}750}{4{,}500} = 1.5. Multiplying by the same factor each month means the users grow by the same percentage, 50%50\%, which is exponential growth.

Choice A is tempting because the first increase is a round 1,0001{,}000, but the later increases are 1,5001{,}500 and 2,2502{,}250.

Why the other choices are wrong

  • A. The increases are 1,000, then 1,500, then 2,250, so the amount added each month is not constant.
  • B. Growth by the same percentage each month is exponential, not linear.
  • C. The amounts added each month are different; it is the growth factor, 1.5, that stays the same.
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