Mathematics Grade 9 15 min

Geometric sequences with fractions

Geometric sequences with fractions

Tutorial Preview

1

Introduction & Learning Objectives

Learning Objectives Identify if a sequence containing fractions is geometric. Calculate the common ratio (r) when it is a fraction. Determine the next term in a geometric sequence involving fractions. Use the general term formula, a_n = a_1 * r^(n-1), to find a specific term when a_1 and/or r are fractions. Determine a missing term within a geometric sequence of fractions. Set up and solve simple real-world problems that model geometric sequences with fractions. Imagine a pizza is shared so that each person takes 1/3 of the remaining amount. How much is left for the 4th person? 🍕 This tutorial explores geometric sequences where the numbers are fractions or the pattern involves multiplying by a fraction. Understanding these sequences is crucial for grasping concepts like ex...
2

Key Concepts & Vocabulary

TermDefinitionExample Geometric SequenceA sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number.The sequence 32, 16, 8, 4, ... is geometric because you multiply by 1/2 each time. Term (a_n)Each individual number in a sequence. We use a_1 for the first term, a_2 for the second, and a_n for the nth term.In the sequence 1/2, 1/4, 1/8, the third term (a_3) is 1/8. Common Ratio (r)The constant factor you multiply by to get from one term to the next. It is found by dividing any term by its preceding term.In the sequence 81, 27, 9, ..., the common ratio is r = 27/81 = 1/3. First Term (a_1)The starting value or the very first number in a sequence.In 1/5, 1/10, 1/20, ..., the first term (a_1) is 1/5. Fractional RatioA common ratio...
3

Core Formulas

Finding the Common Ratio (r) r = a_n / a_{n-1} To find the common ratio, divide any term by the term that comes directly before it. This is the key to proving a sequence is geometric and finding the pattern. The General Term Formula a_n = a_1 * r^(n-1) This formula allows you to find any term (a_n) in a geometric sequence if you know the first term (a_1), the common ratio (r), and the term number you want (n).

4 more steps in this tutorial

Sign up free to access the complete tutorial with worked examples and practice.

Sign Up Free to Continue

Sample Practice Questions

Challenging
In the geometric sequence 128, 64, 32, ..., which term is equal to 1/2?
A.The 8th term
B.The 7th term
C.The 10th term
D.The 9th term
Challenging
Three consecutive terms in a geometric sequence are 4/3, x, and 3/16. What is the value of the missing term, x?
A.1/4
B.1/2
C.3/4
D.2/3
Challenging
Sequence A is a geometric sequence starting with 27 and a common ratio of 1/3. Sequence B is a geometric sequence starting with 1/3 and a common ratio of 3. At which term number (n) will the terms of both sequences be equal?
A.n=3
B.n=2
C.n=4
D.n=5

Want to practice and check your answers?

Sign up to access all questions with instant feedback, explanations, and progress tracking.

Start Practicing Free

More from Rational functions and expressions

Ready to find your learning gaps?

Take a free diagnostic test and get a personalized learning plan in minutes.