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Geometric Sequences

12 practice questions with full worked solutions. Free, no account needed.

Problems & worked solutions

Problem #0282 International

Problem 1 Geometric Sequences

The numbers 4,12,36,108, form a geometric progression. The common ratio q equals:

Show answer & worked solution
  1. A. 2
  2. B. 13
  3. C. 3✓ correct
  4. D. 4

q=b2b1=124=3.

Problem #0281 International

Problem 2 Geometric Sequences

In the geometric progression (bn)n1, b1=2 and q=3. Determine b5.

Show answer & worked solution
  1. A. 54
  2. B. 81
  3. C. 162✓ correct
  4. D. 486

b5=b1q4=234=281=162.

Problem #0006 International

Problem 3 Series

What is the sum of the infinite geometric series 1+12+14+?

Show answer & worked solution
  1. A. 32
  2. B. 2✓ correct
  3. C. 52
  4. D. Diverges

Geometric series with a=1, r=12. Sum =a1r=111/2=2.

Problem #0012 International

Problem 4 Sum of Terms

Compute k=052k.

Show answer & worked solution
  1. A. 31
  2. B. 62
  3. C. 63✓ correct
  4. D. 127

With r=2 and n=5: 26121=631=63. (Check: 1+2+4+8+16+32=63.)

Problem #0287 International

Problem 5 Geometric Sequences

A bank deposit of $1,000 earns annual compound interest at 10%. After 3 years, the balance is closest to:

Show answer & worked solution
  1. A. $1,300
  2. B. $1,320
  3. C. $1,331✓ correct
  4. D. $1,350

A=10001.13=10001.331=$1,331.

Problem #0285 International

Problem 6 Geometric Sequences

In a geometric progression with b1=5 and q=2, the term bn=320. Determine n.

Show answer & worked solution
  1. A. 5
  2. B. 6
  3. C. 7✓ correct
  4. D. 8

52n1=3202n1=64=26n1=6n=7.

Problem #0286 International

Problem 7 Geometric Sequences

Compute the sum 1+12+14+18+.

Show answer & worked solution
  1. A. 32
  2. B. 2✓ correct
  3. C. 52
  4. D.

b1=1, q=12: S=111/2=2.

Problem #0283 International

Problem 8 Geometric Sequences

Compute the sum of the first 10 terms of the geometric progression 1,2,4,8,.

Show answer & worked solution
  1. A. 511
  2. B. 512
  3. C. 1023✓ correct
  4. D. 1024

S10=1210121=1023.

Problem #0284 International

Problem 9 Geometric Sequences

The numbers 3, x, 27 are in geometric progression (with positive ratio). Determine x.

Show answer & worked solution
  1. A. 5
  2. B. 9✓ correct
  3. C. 15
  4. D. 30

x2=327=81x=9 (positive ratio).

Problem #0290 International

Problem 10 Geometric Sequences

For the geometric progression 1,2,4,8,16,32,, the sum b2+b4+b6 equals:

Show answer & worked solution
  1. A. 36
  2. B. 42✓ correct
  3. C. 48
  4. D. 56

b2=2, b4=8, b6=32. The sum is 2+8+32=42. (These three form a GP with first term 2 and ratio 4.)

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