Arithmetic
Geometric
Which Form?
Recursive and Explicit Rules
Sequences in Context
100

What is the common difference of the sequence?

5, 9, 13, 17,… 

4

100

What is the common ratio?

4, 12, 36, 108,… 

3

100

A theater adds 4 seats to each new row. The first row has 20 seats.Which form would be most useful for finding the number of seats in the next row based on the previous row?

Recursive

100

Write a recursive rule for:

7, 11, 15, 19,… 

f(1)=7 

f(n)=f(n−1)+4

100

The amount of medication administered on day n is represented by M(n). M(1)=2000; M(n)=0.75M(n−1). What does M(4) represent?

A. Amount of medication administered over 4 days
B. The amount of medication administered on Day 4
C. The number of days medication was administered
D. 75% of the medication administered on Day 4

B

200

Find the next two terms:

24, 12, 0, −12,… 

−24, −36


200

Find the next two terms:

2000, 1000, 500, 250,… 

125, 62.5

200

A student saves $15 each week and starts with $40. She wants to find how much money she will have after 20 weeks without calculating the amount saved each week. Which form would be most efficient?

Explicit

200

Find the explicit formula:

8, 13, 18, 23,… 

f(n) = 8+5(n-1)

200

A population of bacteria is modeled by P(n) = 500(2)^(n-1)  where n represents the number of hours. What will the population be after 6 hours?

16,000

300

Find the 10th term:

4, 11, 18, 25,…


67

300

Which sequence is geometric?
A. 2,5,9,14,…
B.  1/4,1,4,16
C. 5,7,9,11,…
D. 520,420,320,220,…

B

300

A medication dosage decreases by multiplying the previous day's dosage by 0.75. The doctor wants to calculate the dosage for the next day using the current day's dosage. Which form would be most appropriate?

Recursive

300

Write a recursive rule for:

3, 9, 27, 81,… 

f(1)=3

 f(n)=3f(n−1)

300

A student is saving money for a car. The amount of money in the account after nn weeks is modeled by A(n)=50+15(n−1) where A(n) represents the amount of money saved after n weeks. How much money will the student have after 12 weeks?

215

400

Write an explicit formula for:

6, 10, 14, 18,… 

f(n) = 6+4(n-1)

400

𝑓(1) = 3000, 𝑓(2) = 2250, 𝑓(3) = 1687.5, 𝑓(4) = 1265.625, 𝑓(5) = 949.21875

What is the common ratio?

0.75

400

A school is adding lights to a stage backdrop. The first row has 30 lights, and each new row has 6 more lights than the previous row. The teacher wants to determine the number of lights needed for the 25th row directly, without finding the number of lights in rows 2–24. Which form would be most useful?

Explicit

400

Write an explicit formula for:

5, -10, 20, -40,… 

g(n) = 5(-2) ^ (n-1)

400

A school is adding 7 chairs to each new row. The number of chairs is modeled recursively: C(1)=18; C(n)=C(n−1)+7. How many chairs will be in the 9th row?

74

500

An arithmetic sequence has f(1)=35 and a common difference of −7. Find f(12).

-42

500

A geometric sequence has g(1)=48 and a common ratio of  1/2 . Find g(7).

3/4

500

A sequence is defined f(1)=2, f(n)=3f(n−1).

What is f(4)?

54

500

A sequence has f(1)=10 and f(n)=f(n−1)+6.

Which explicit formula represents the sequence?

f(n)=10+6(n-1)

500

Sequence A has values: 3, 8, 13, 18, 23,…  Sequence B has values: 1/25, 1/5, 1, 5, 25, ...  Which sequence will have the greater 9th term? By how much?

B by 15,625-43=15,582