# The sum of the squares of the first ten natural numbers is, # 1^2 + 2^2 + ... + 10^2 = 385 # The square of the sum of the first ten natural numbers is, # (1 + 2 + ... + 10)^2 = 55^2 = 3025 # Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640. # Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum. # Notes: # Sum of the squares: (n(n+1)(2n+1)) / 6 # Square of the sum: (n(n+1) / 2 ) * (n(n+1) / 2 ) require "benchmark" def differenceSSBetweenSS(number) sumOfSquare = (number * (number + 1) * (2 * number + 1)) / 6 squareOfSum = (number * (number + 1) / 2) * (number * (number + 1) / 2) squareOfSum - sumOfSquare end time = Benchmark.realtime do puts differenceSSBetweenSS(100) end puts "Time elasped #{time*1000} milliseconds" # Output: # 25164150 # Time elasped 0.044 milliseconds