Posted by **Riana** on Tuesday, January 1, 2013 at 7:56pm.

bricks are stacked in 20 rows such that each row has a fixed number of bricks more than the row above it. the top row has 5 bricks and the bottom row 62 bricks. how many bricks are in the stack?

- math -
**Reiny**, Tuesday, January 1, 2013 at 8:03pm
using your arithmetic sequence definitions

t1 = a = 5

t20 = a+19d = 62

5+19d = 62

19d = 57

d = 3

sum(20) = (20/2)(first + last)

= 10(5+62) = 670

- math -
**Riana**, Tuesday, January 1, 2013 at 8:15pm
how did you gt 19d ?

- math -
**Reiny**, Tuesday, January 1, 2013 at 8:23pm
The formula for

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

so term(20) = a+19d

You MUST know these to be able to work with sequences

## Answer this Question

## Related Questions

- MATH - a pile of bricks has 85 bricks in the bottom row, 79 bricks in the second...
- Math - A pile of bricks has 85 bricks in the bottom row, 81 bricks in the second...
- math - Task is to construct two brick columns of the dimensions shown on which ...
- Math - Mike bought 252 bricks to build a wall in his yard. Each row has 14 ...
- Math - Julia wants to build another garden wall, 10 bricks long and 3 bricks ...
- maths - A brick wall is built by using 2 bricks less in each layer than in the ...
- Advanced Math - Find DE if matrix D= Row 1= -2,4,6 and ROW 2= 5,-7,1 and matrix ...
- trigonometry - Find the number of cans stacked in a display if there are 30 rows...
- Math - an auditorium has 50 rows of seats. THe first row has 20 seats, the row ...
- Math - The first row of a concert hall has 25 seats and each row after the first...