Problema Solution

To go to sleep, Oliver counted by 6s starting from 15. Thus the first few numbers he named were 15,21,27,33,...The last number he named before he fell asleep was 363. How many numbers did Oliver name?

Answer provided by our tutors

Arithmetic progression (AP) or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant.


We have the following arithmetic progression:


a0 = 15


d = 6


an = a0 + n*d


an = 15 + 6n


If an = 363 we have:


15 + 6n = 363

........


click here to see all the equation solution steps


........

n = 58


Including the first number Oliver counted 58 + 1 = 59 numbers.