Help with an ACT question (math)?

Test Preparation ACT Preparation
1

<p>Patrick celebrated the New ear by buying 3 DVDs during the month of January. In each subsequent month, he planned to buy 5 more DVDs than he had bought the month before. How many DVDs did Patrick buy for the entire year?</p>

<p>a)58
b)61
c)91
d)330
e)336</p>

<p>Please show me how you arrived at your answer, and if there is a shorter method than just adding it all. Thank you!</p>

2

<p>I think it should be 366! If it is, then you could use the equation for the sum of an arithmetic sequence, which is (n(a1+an))/2. In other words, (12(3+58))/2=366</p>