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Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

$10,20,40,80$ is an example of

  1. fibonacci sequence

  2. harmonic sequence

  3. arithmetic sequence

  4. geometric sequence
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$10, 20, 40, 80$ is an example of geometric sequence.
In geometric sequence, the ratio of succeeding term to the preceeding term is always equal.

Here the common ratio is $2$.

Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

Identify the geometric series.

  1. $1 + 3 + 5 + 7 +....$
  2. $2 + 12 + 72 + 432...$
  3. $2 + 3 + 4 + 5 +...$
  4. $11 + 22 + 33 + 44+...$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Geometric series is of the following form:

$a+ar+ar^2+ar^3 +ar^4+..........+ar^n$
Series $2+12+72+432+......$ follows the same with $a=2$ and $r=6$.
Hence, option B is correct.

Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

$1, 3, 9, 27, 81$ is a

  1. geometric sequence

  2. arithmetic progression

  3. harmonic sequence

  4. geometric series
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$1, 3, 9, 27, 81$ is a geometric sequence.
A geometric progression is a sequence of numbers such that the quotient of any two successive members of the sequence is a constant called the common ratio of the sequence.

Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

$4, \dfrac{8}{3}, \dfrac{16}{9}, \dfrac{32}{27}..$ is a

  1. arithmetic sequence

  2. geometric sequence

  3. geometric series

  4. harmonic sequence
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

lets check the ratio between the consecutive terms.
$\dfrac {\frac {8}{3}}{4}=\dfrac {8}{12}=\dfrac {2}{3}$
Again take the ratio between next consecutive terms.
$\dfrac {\frac {16}{9}}{\frac {8}{3}}=\dfrac {16\times 3}{9\times 8}=\dfrac {2}{3}$
Here the common ratio is same $\dfrac{2}{3}$ throughout.
Hence, $4, \dfrac{8}{3}, \dfrac{16}{9}, \dfrac{32}{27}..$ is a geometric sequence.

Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

In a _______ each term is found by multiplying the previous term by a constant.

  1. geometric sequence

  2. arithmetic sequence

  3. geometric series

  4. harmonic sequence
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Sol:
We know that if a,b,c are in G.p then $b^2=ac$
We know that a G.P
$a,ar,ar^2.ar^3-----ar^n$
${ a } _{ 1 }{ ,a } _{ 2 },{ a } _{ 3 },{ a } _{ 4 },----{ a } _{ n }$
$\dfrac { { a } _{ 2 } }{ { a } _{ 1 } } =\dfrac { { a } _{ 3 } }{ { a } _{ 2 } } =\dfrac { { a } _{ 3 } }{ { a } _{ 3 } } ----\dfrac { { a } _{ n } }{ { a } _{ n-1 } } =r$  (r=constant)
Therefore in a geometric progression each term is found multiplying the previous term by constant .
Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

If a sequence of values follows a pattern of multiplying a fixed amount times each term to arrive at the following term, it is called a: 

  1. geometric sequence

  2. arithmetic sequence

  3. geometric series

  4. harmonic sequence
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$3,3^2,3^3,3^4,....(r=3)$
In a sequence if a fixed amount/constant is multiplied to each term to get the successive term the sequence is called geometric sequence.
Here $3$ is the constant which gets multiplied to each term to obtain the successive term.
Multiple choice maths geometric sequences introduction to geometric progression understanding geometric progressions introduction to geometric progressions

Identify the geometric progression.

  1. $1, 3, 5, 7, 9, ...$
  2. $2, 4, 6, 8, 10...$
  3. $5, 10, 15, 25, 35..$
  4. $1, 3, 9, 27, 81...$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A geometric sequence is a sequence of numbers such that the quotient of any two successive members of the sequence is a constant called the common ratio of the sequence.
So, $1, 3, 9, 27, 81...$ is a geometric progression.
Here the common ratio is $3$.