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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 TypeMathematical ExpressionDescriptionExample (1-5)Result
Sum of First n Natural NumbersSₙ = n(n+1)/2Sum of consecutive integers from 1 to nS₅ = 5(6)/215
Sum of SquaresSₙ² = n(n+1)(2n+1)/6Sum of squares from 1² to n²S₅² = 5(6)(11)/655
Sum of CubesSₙ³ = [n(n+1)/2]²Sum of cubes from 1³ to n³S₅³ = [15]²225
Arithmetic Sequenceaₙ = a₁ + (n-1)dnth term where d=1a₅ = 1 + (5-1)×15
Arithmetic SeriesSₙ = n/2[2a₁ + (n-1)d]Sum of arithmetic sequenceS₅ = 5/2[2 + 4]15
Average FormulaAverage = (First + Last)/2Mean of consecutive integers(1 + 5)/23
Product FormulaP = n!Product of first n natural numbers5! = 5×4×3×2×1120

For Sequence 1-2-3-4-5-6-7-8-9-10

PropertyFormulaCalculationResult
SumS₁₀ = 10(11)/210 × 11 ÷ 255
Sum of SquaresS₁₀² = 10(11)(21)/610 × 11 × 21 ÷ 6385
Sum of CubesS₁₀³ = [55]²55²3025
Average(1 + 10)/211 ÷ 25.5

For Sequence 1-2-3-4-5-6-7

PropertyFormulaCalculationResult
SumS₇ = 7(8)/27 × 8 ÷ 228
Sum of SquaresS₇² = 7(8)(15)/67 × 8 × 15 ÷ 6140
Average(1 + 7)/28 ÷ 24

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

  1. Symmetry: The sequence is symmetric around its median (3)
  2. Linear Growth: Each term increases by 1
  3. Sum Property: Sum equals the middle term × number of terms
  4. Perfect Relationships:
    • 1 + 5 = 2 + 4 (outer terms equal inner terms)
    • Sum of cubes equals square of sum

Important Identities

IdentityMathematical ExpressionVerification
Sum = Middle × CountFor odd n: Sum = middle × n3 × 5 = 15 ✓
Cube Sum Identity(1³ + 2³ + ... + n³) = (1 + 2 + ... + n)²225 = 15² ✓
Even-Odd RelationshipSum of n odds = n²1+3+5+7+9 = 25 = 5² ✓
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