The sum of the fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first 15 terms of
the arithmetic progression?
A. 300
B. 120
C. 150
D. 170
E. 270
Sum_progessions
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Hello.
I need some help understanding this solution.
what is a(n)=a(1)+(n-1)d ?. Is that formula to know for the gmat. If so, can someone please explain it to me?
I would appreciate any help.
Thanks
I need some help understanding this solution.
what is a(n)=a(1)+(n-1)d ?. Is that formula to know for the gmat. If so, can someone please explain it to me?
I would appreciate any help.
Thanks
ODOD
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If the sum of the 4th and 12th term is 20, so is the sum of the 1st and 15th. Thus we have 15 terms that have a mean of 20/2 = 10. Sum= 150gmatmachoman wrote:The sum of the fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first 15 terms of
the arithmetic progression?
A. 300
B. 120
C. 150
D. 170
E. 270
Kevin Armstrong
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Here a link to the formula used from wikipedia... Might shed some light
https://en.wikipedia.org/wiki/Arithmetic_progression
https://en.wikipedia.org/wiki/Arithmetic_progression