Posted by **Jnr John** on Tuesday, April 16, 2013 at 11:29pm.

A display of cans on a grocery shelf consists of 20 cans on the bottom, 18 cans in the next row, and so on in an arithmetic sequence, until the top row has 4 cans. How many cans, in total, are in the display?

- Please Help!! Math -
**Reiny**, Tuesday, April 16, 2013 at 11:36pm
terms of the sequence:

20 , 18 , 16 ,...4

So we have a = 20, d = -2 , t(n) = 4

t(n) = a + (n-1)d

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

-16 = -2n + 2

2n = 18

n = 9

so we need sum of 9 terms

= (9/2)(first + last)= (9/2)(20 + 4) = 108

or

Sum(n) = (n/2)(2a + (n-1)d)

= (9/2)(40 + 8(-2)) = 108

check:

term9 = a = 8d

= 20 + 8(-2) = 20-16 = 4

## Answer this Question

## Related Questions

- maths - find a6 for an arithmetic sequence where a1=3x+1 and d=2x+6. 2.A display...
- math - If Jenny built a triangle out of soup cans and there are 4 at the top row...
- trigonometry - Find the number of cans stacked in a display if there are 30 rows...
- Math - a grocery clerk nstacks three rows of can of fruit for a display, each of...
- arithmetic - You have 798 cans in 19 rows. If the cans are placed so that each ...
- math - There are eight shelves. How many soup cans a grocery clerk stack if the ...
- 4th grade math - A store clerk wants to stack 55 cans of tennis balls in a ...
- Algebra/Math - Can you check these for me. Directions: Find the slope of the ...
- Math - 7^2006 Solving problems with "to the power of" IT works better if you ...
- Math - The Recycling Department of a fast food chain is planning to have a ...