IBEW Number Series 2 — Questions and Answers
Question 1: What is the next number in the series: 3, 6, 12, 24, 48, ___?
- 72
- 84
- 96 (Correct answer)
- 64
Correct answer: 96
Each term is multiplied by 2: 3×2=6, 6×2=12, 12×2=24, 24×2=48, 48×2=96.
This is a geometric series with a common ratio of 2. Starting at 3, each term doubles: 3, 6, 12, 24, 48, 96. Geometric sequences are identified when dividing any term by the previous term gives the same constant ratio.
Question 2: Complete the series: 100, 91, 83, 76, 70, ___?
- 64
- 65 (Correct answer)
- 66
- 63
Correct answer: 65
The differences decrease by 1 each step: -9, -8, -7, -6, so next difference is -5: 70-5=65.
The differences between terms are: 100-91=9, 91-83=8, 83-76=7, 76-70=6. The differences decrease by 1 each time, so the next difference is 5. Thus 70-5=65. This is an arithmetic series of differences.
Question 3: Find the missing number: 2, 5, 11, 23, ___, 95
- 44
- 46
- 47 (Correct answer)
- 45
Correct answer: 47
Each term is doubled and 1 is added: 2×2+1=5, 5×2+1=11, 11×2+1=23, 23×2+1=47.
The rule is: next term = (current term × 2) + 1. Verification: 2×2+1=5 ✓, 5×2+1=11 ✓, 11×2+1=23 ✓, 23×2+1=47, 47×2+1=95 ✓. This is a combined multiplication-and-addition pattern.
Question 4: What comes next: 1, 4, 9, 16, 25, ___?
- 30
- 36 (Correct answer)
- 32
- 34
Correct answer: 36
These are perfect squares: 1²=1, 2²=4, 3²=9, 4²=16, 5²=25, 6²=36.
The series consists of perfect squares: 1=1², 4=2², 9=3², 16=4², 25=5². The next term is 6²=36. Recognizing common mathematical sequences like squares, cubes, and primes is essential for IBEW aptitude tests.
Question 5: Identify the next term: 7, 14, 28, 56, 112, ___?
- 168
- 196
- 224 (Correct answer)
- 200
Correct answer: 224
Each term is multiplied by 2: 112×2=224.
This geometric sequence has a common ratio of 2. Each term is double the previous: 7, 14, 28, 56, 112, 224. The common ratio can be verified: 14÷7=2, 28÷14=2, 56÷28=2, 112÷56=2, so 112×2=224.
Question 6: What is the missing number: 5, 10, 20, ___, 80, 160?
- 35
- 40 (Correct answer)
- 45
- 30
Correct answer: 40
Each term is doubled: 5, 10, 20, 40, 80, 160.
The series follows the rule of multiplying by 2 each time: 5×2=10, 10×2=20, 20×2=40, 40×2=80, 80×2=160. The missing number is 40. This type of geometric doubling sequence is common on IBEW aptitude tests.
IBEW Number Series 2
What is the next number in the series: 3, 6, 12, 24, 48, ___?