Saturday

November 22, 2014

November 22, 2014

Posted by **simranpreet** on Monday, December 3, 2012 at 6:16am.

please help this questions please.

- maths -
**Reiny**, Monday, December 3, 2012 at 9:43amsum of 8 terms is 156

(8/2)(2a + 7d) = 156

4(2a + 7d) = 156

2a + 7d = 39

(a+11d) : (a + 67d) = 1 : 5

(a+11d)/(a+67d) = 1/5

5a + 55d = a + 67d

4a = 12d

a = 3d

sub that into 2a+7d=39

6d + 7d = 39

13d=39**d=3 , then in a = 3d ---> a = 9**

first term is 9

term 15 = a+14d = 9+14(3) = 51

check:

sum(8) = (8/2)(18 + 7(3)) = 4(39) = 156 , checks !

term12 = a+11d = 42

term 68 = a+67d = 210

and 42/210 = 1/5 , YEahh!

**Answer this Question**

**Related Questions**

Maths - 1..The first 2 terms of a geometric progression are the same as the ...

maths - 1) The first term of arithmetic progression is -20 and the sum of it's ...

arithmetic - Each term of a progression is determined by adding 0.5 to the ...

Maths - Arithmetic Progression - The fourth term of an AP is 8 and the sum of ...

maths - The thirteenth term of an arithmetic progrssion os 27 and the seventh ...

maths - The thirteenth term of an arithmetic progrssion os 27 and the seventh ...

Precalculus - The 8th term in an arithmetic sequence is 5, and the sum of the ...

GP Caluculus - The third term of a geometric progression is 16. The sum of the ...

Math Algebra - The first term of a geometric progression is more than the third ...

math - the fourth term of an arithmetic progression is equal to 3 times the ...