An algebra problem by Mohammad Khaza

Algebra Level pending

The sum of first 12 terms of an arithmetic progression is 144, and the sum of the first 20 terms of the same progression is 560.

What is the sum of first 6 terms of this same progression?


The answer is 0.

Mohammad Khaza by Mohammad Khaza , 20, Bangladesh

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1 solution

Ahmad Saad
Jul 22, 2017

Let first term = a , common difference = d

144 = 6(2a + 11d) , 560 = 10(2a + 19d)

a = -10 , d = 4 ---> sum of first 6 terms = 3(2×(-10) + 5×4) = 0

2 Helpful 0 Interesting 0 Brilliant 0 Confused

at last i got a solution but it would have been more good with clear explanation.as i don't know all the latex technique for this question ,i am unable to post a solution for this.

Mohammad Khaza - 3 years, 10 months ago

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