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Q.
What is the name of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10?
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Detailed Solution
The sequence 1, 2, 3, 4, 5 represents the foundation of many mathematical concepts. This comprehensive guide covers all essential formulas related to consecutive integers, arithmetic sequences, and their applications.
Core Formulas Table
| Formula Type | Mathematical Expression | Description | Example (1-5) | Result |
| Sum of First n Natural Numbers | Sₙ = n(n+1)/2 | Sum of consecutive integers from 1 to n | S₅ = 5(6)/2 | 15 |
| Sum of Squares | Sₙ² = n(n+1)(2n+1)/6 | Sum of squares from 1² to n² | S₅² = 5(6)(11)/6 | 55 |
| Sum of Cubes | Sₙ³ = [n(n+1)/2]² | Sum of cubes from 1³ to n³ | S₅³ = [15]² | 225 |
| Arithmetic Sequence | aₙ = a₁ + (n-1)d | nth term where d=1 | a₅ = 1 + (5-1)×1 | 5 |
| Arithmetic Series | Sₙ = n/2[2a₁ + (n-1)d] | Sum of arithmetic sequence | S₅ = 5/2[2 + 4] | 15 |
| Average Formula | Average = (First + Last)/2 | Mean of consecutive integers | (1 + 5)/2 | 3 |
| Product Formula | P = n! | Product of first n natural numbers | 5! = 5×4×3×2×1 | 120 |
For Sequence 1-2-3-4-5-6-7-8-9-10
| Property | Formula | Calculation | Result |
| Sum | S₁₀ = 10(11)/2 | 10 × 11 ÷ 2 | 55 |
| Sum of Squares | S₁₀² = 10(11)(21)/6 | 10 × 11 × 21 ÷ 6 | 385 |
| Sum of Cubes | S₁₀³ = [55]² | 55² | 3025 |
| Average | (1 + 10)/2 | 11 ÷ 2 | 5.5 |
For Sequence 1-2-3-4-5-6-7
| Property | Formula | Calculation | Result |
| Sum | S₇ = 7(8)/2 | 7 × 8 ÷ 2 | 28 |
| Sum of Squares | S₇² = 7(8)(15)/6 | 7 × 8 × 15 ÷ 6 | 140 |
| Average | (1 + 7)/2 | 8 ÷ 2 | 4 |
Special Pattern Formulas
Triangular Numbers (1, 3, 6, 10, 15...)
- Formula: Tₙ = n(n+1)/2
- For position 5: T₅ = 5(6)/2 = 15
Square Numbers (1, 4, 9, 16, 25...)
- Formula: Sₙ = n²
- For position 5: S₅ = 5² = 25
Pentagonal Numbers
- Formula: Pₙ = n(3n-1)/2
- For position 5: P₅ = 5(14)/2 = 35
Advanced Applications
Sum from 1 to 100 Formula
- Formula: S₁₀₀ = 100(101)/2 = 5,050
- Historical Note: This is famously attributed to Gauss's childhood calculation
General Range Formula (Sum from a to b)
- Formula: Sum = (b-a+1)(a+b)/2
- Example (1 to 5): (5-1+1)(1+5)/2 = 5×6/2 = 15
Consecutive Even Numbers (2, 4, 6, 8, 10)
- Formula: Sum = n(n+1)
- For 5 terms: 5(6) = 30
Consecutive Odd Numbers (1, 3, 5, 7, 9)
- Formula: Sum = n²
- For 5 terms: 5² = 25
Mathematical Relationships
Key Properties of 1-2-3-4-5 Sequence
- Symmetry: The sequence is symmetric around its median (3)
- Linear Growth: Each term increases by 1
- Sum Property: Sum equals the middle term × number of terms
- Perfect Relationships:
- 1 + 5 = 2 + 4 (outer terms equal inner terms)
- Sum of cubes equals square of sum
Important Identities
| Identity | Mathematical Expression | Verification |
| Sum = Middle × Count | For odd n: Sum = middle × n | 3 × 5 = 15 ✓ |
| Cube Sum Identity | (1³ + 2³ + ... + n³) = (1 + 2 + ... + n)² | 225 = 15² ✓ |
| Even-Odd Relationship | Sum of n odds = n² | 1+3+5+7+9 = 25 = 5² ✓ |
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