Question

A display of cans in a grocery store consists of 15 rows. There are 45 cans on the bottom , 42 cans on the next row, and so on, How many cans did they use in the display?​

Answer 1

Answer:

n = 9

Step-by-step explanation:

20 + 18 + ... + 6 + 4

---------------------------

a = 20 ; d = -2 ; n = ?

--------

4 = 20 + (n-1)(-2)

-16 = (n-1)(-2)

---------

n-1 = 8

n = 9

-------

S(9) = (9/2)(20+4)

S(9) = 4.5*24

S(9) = 108