Tuesday

November 25, 2014

November 25, 2014

Posted by **Marcel** on Thursday, February 11, 2010 at 12:53am.

- arithmetic -
**Reiny**, Thursday, February 11, 2010 at 8:03amThis is an arithmetic series

You know S_{19}, n=19, d=-3

You don't know "a".

S_{19}= (n/2)[2a + (n-1)d]

798 = 19/2(2a + 18(-3)]

1596 = 38a - 1026

2633 = 38a

a = 69

So depending on whether your bottom row is the

first or the 69th, it would be either 69 or

69 + 18(-3) = 15

check:

69 + 66 + 63 + ... + 15 for 19 terms

= 19(first+last)/2 = (19)(69+15)/2 = 798

**Answer this Question**

**Related Questions**

Please Help!! Math - A display of cans on a grocery shelf consists of 20 cans on...

Math - a grocery clerk nstacks three rows of can of fruit for a display, each of...

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...

Algebra/Math - Can you check these for me. Directions: Find the slope of the ...

Math - The Recycling Department of a fast food chain is planning to have a ...

math - Chef Fabio went to the store and bought 2 cans of beans, 2 cans of ...

maths - Chef Fabio went to the store and bought 2 cans of beans, 2 cans of ...

Math - 7^2006 Solving problems with "to the power of" IT works better if you ...