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August 23, 2014

August 23, 2014

Posted by **Anonymous** on Monday, December 27, 2010 at 10:17am.

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

- Math -
**Dr Russ**, Monday, December 27, 2010 at 10:30amI 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

- Math -
**Anonymous**, Monday, December 27, 2010 at 10:42amRight, instead of using the Sn formula. I could have just use an = a1 + (n - 1) d

Thanks a lot

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