Question

On each of ner birthdays. Bernadette blew out a number of candles

equal to her age in years. She lived to be 107. How many candles
did she blow out during her lifetime? (She had some help the first
few years but they all count)

Answer 1

5778

Explanation:

1+2+3+4+5+....+105+106+107

The sequence of numbers (1, 2, 3, … , 107) is arithmetic and when we are looking for the sum of a sequence, we call it a series. Thanks to Gauss, there is a special formula we can use to find the sum of a series:

S=n(n+1)/2=11556÷2=5778

S is the sum of the series and n is the number of terms in the series, in this case, 107

There are other ways to solve:

This is an arithmetic series, for which the formula is:

S = n[2a+(n-1)d]/2

where a is the first term, d is the difference between terms, and n is the number of terms.

For the sum of the first 107 whole numbers:

a = 1, d = 1, and n = 107

Therefore, sub into the formula:

S = 107[2(1)+(107-1)(1)]/2 =

107(2+106)/2=107*108/2=5778

so she blow out 5778 candless during her lifetime