Adisplay 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?

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

529 and 531

step-by-step explanation:

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