Cogito
Integrated Math 1 · Chapter 5 · Lesson 1
Arithmetic Sequences
Adding the same amount each time.
12 problems · about 20 minutes · F-BF.A.2, F-LE.A.2
Figure — use these to answer the problems
Warm Up
Straightforward practice. Get the method working first.
5 problemsa₁ = 5, d = 4. What is the 10th term?
AnswerWhy does the formula use n − 1 rather than n?
- Reaching the nth term takes one fewer step than n.
- Because sequences start at zero.
2, 5, 8, 11. Common difference?
Answer20, 15, 10, 5. Common difference?
Answera₁ = 4, d = 3. What is the 10th term?
Answer
Build It Up
The same ideas with more to keep track of.
3 problemsa₁ = 100, d = −7. What is the 5th term?
AnswerTo reach the 12th term, how many steps from the first?
Answera₁ = 6, d = 5. What is the 8th term?
Answer
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsSort each sequence by whether it is arithmetic.
Write each item under the heading it belongs to: 4, 9, 14, 19 · 30, 24, 18, 12 · 2, 4, 8, 16 · 1, 4, 9, 16
Arithmetic
Not arithmetic
a₁ = 2, d = 6. What is the 15th term?
AnswerThe Difference
5, 12, 19, 26. What is the common difference?
AnswerThe Term
a₁ = 3 and d = 4. What is the 20th term?
Answer