Question

What would be the total number of days she used the gym membership in week 10?

Answer 1

We can see that each time the number in the sequence increases by 5, so this is a arithmetic progression.

The formula for the n-th term of an arithmetic progression is:

`a_n=a_1+(n-1)\cdot r`

The first term is 4, and the rate is 5, so we have that:

`a_n=4+(n-1)\cdot5`

If we want to find the 10th term, we just need to use n = 10:

`\begin{gathered} a_(10)=4+(10-1)\cdot5 \\ a_(10)=4+9\cdot5 \\ a_(10)=4+45 \\ a_(10)=49 \end{gathered}`

So Breanna would use her gym membership 49 days in week 10.