### Discussion :: Numbers - General Questions (Q.No.20)

Bill said: (Apr 14, 2011) | |

Help me to find even more easy way. |

K.Pavan said: (May 31, 2012) | |

n/2 * (a+L) where L is the last term that is 45.a is the first term that is 1. since natural numbers start from 1 |

Puneet said: (Jun 9, 2013) | |

[N/2]*(first term + last term). |

Rohit Singla said: (Nov 14, 2014) | |

Middle no.of 45 is 23. So its average is also 23. 23*45 = 1035. |

Piyosh said: (Jan 16, 2016) | |

Is this n(n+1)/2 applicable for all A.P? |

Smiley said: (Jun 22, 2016) | |

Does the shortcut method work in every case? |

Rohan said: (Jul 1, 2016) | |

@Rohit, I like your method quit interesting. |

Vinayak said: (Jul 9, 2016) | |

@Rohit. I like your method it's a simple thing to get an answer. |

Bimal said: (Jul 28, 2016) | |

Sum upto nth of natural numbers = n* (n + 1)/2, Put n = 45 here. |

Manali said: (Nov 9, 2016) | |

Simplest way to multiply the given number with its consecutive number and then divide by 2. i.e (45 * 46)/2 = 1035. |

Tohid said: (Jun 3, 2017) | |

n(n + 1)÷2 = 45(45 + 1)÷2 = 1035. |

Rinkal said: (Dec 12, 2017) | |

I like your method, thanks @Rohit. |

Jignesh said: (Jan 4, 2018) | |

Good method @Rohit. |

Md Ikramul Haque said: (Jul 24, 2018) | |

4+5=9. And 1035=1+0+3+5=9. Answer is A. |

Ninjahari said: (Jul 15, 2019) | |

n(n+1)/2 is applicable. Am I right? |

Bhartari Shinde said: (Jul 20, 2019) | |

n(n+1)/2 = 45(45+1)/2 = 2070/2 = 1035. |

Prasannakumar said: (Nov 16, 2019) | |

If the difference between the same throughout the series at that time only we use: 1) Sum of 'N' natural numbers(Sn) = n(n+1)/2. (Or) 2) Sn = n/2 [2a+(n-1)d] Here, d = difference. n = Total numbers. a = 1st number. Actually AP series is a,a+d,a+2d,a+3d+....+a+(n-1)d. That's why we take a=1. If we take 'x' in place of 'a' in above series, the formula will Become, Sn = n/2 [2x+(n-1)d]. |

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