Question
A pile of bricks has 85 bricks in the bottom row, 81 bricks in the second row up, 77 in the third, and so on up to the top row that contains only 1 brick. How many bricks are in the 12th row?
I don't know if I'm right but I attempted this problem below
c = a1 - d
c = 85 - 4 = 81
- 85 + 81 = 166
Sn = n / 2 (a1 + an)
Sn = 85 / 2 (85 + 166)
Sn = 10667.5
I don't know if I'm right but I attempted this problem below
c = a1 - d
c = 85 - 4 = 81
- 85 + 81 = 166
Sn = n / 2 (a1 + an)
Sn = 85 / 2 (85 + 166)
Sn = 10667.5
Answers
I can't follow you calculation.
Row 1 has
85
Row 2 has
81
row 3 has
77
The nth row will have
85-4(n-1)
so if n=12
then
85-4(12-1)=85-44=41 bricks
Row 1 has
85
Row 2 has
81
row 3 has
77
The nth row will have
85-4(n-1)
so if n=12
then
85-4(12-1)=85-44=41 bricks
Right, instead of using the Sn formula. I could have just use an = a1 + (n - 1) d
Thanks a lot
Thanks a lot
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