<p>Please show how to solve this in as much details as possible. Any plug in strategies ? </p>
<p>During a sale, a customer can buy one shirt for x dollars. Each additional shirt the customer buys costs z dollars less than the first shirt. For example, the cost of the second shirt is x-z dollars. Which of the following represents the customer's cost, in dollars, for n shirts bought during this sale?</p>
<p>Answer: x + (n-1)(x-z)</p>
<p>i think u kinda just have to understand it.</p>
<p>x is 1 shirt
every additional shirt is (x-z)</p>
<p>so x+ (n-1)(x-z) gets you the total price.
if you buy 1 shirt (n=1) then price is x
if you buy 2, x+(x-z)
if you buy 3, x+2(x-z)</p>
<p>use arithmetic progression </p>
<p>Formula = a+(n-1)d</p>
<p>a= the original price
n= n shirts
d= difference in prize which is z</p>
<p>understood thank you so much! :)</p>
<p>
To suit the answer you have provided shouldn’t the question be "n"TH shirT?
Since we aren’t using AP Sum formula here,just 'n’th term formula?</p>
<p>i copied the question exactly from the blue SAT book man. its an official question so i dont know whos right.</p>
<p>which page?</p>
<p>pg 585 number 18</p>
<p>Idk,from the question’s language doesn’t it clearly seem to imply-‘total cost of n shirts’?
ie we should use this formula Sum= n/2{ 2a + (n-1)d }. But with this formula,the answer obv doesnt match.
Damn.Can somebody please clear this?</p>
<p>Whats the exact name for the sum formula ? n/2{ 2a + (n-1)d }</p>
<p>When is it used ?</p>
<p>Its the Arithametic Progressions Sum formula,doesn’t really have any name.</p>
<p>It is used to find the sum of ‘n’ terms of an arithametic progression.
For the term technichalities,see Jwisgod’s post above.</p>