kennethkaunda06
Answered

Welcome to Westonci.ca, your go-to destination for finding answers to all your questions. Join our expert community today! Get detailed answers to your questions from a community of experts dedicated to providing accurate information. Get immediate and reliable solutions to your questions from a community of experienced professionals on our platform.



The sum of the first ten terms of an arithmetic
Progression is 400. If the sum of the first 6
terms of the same series is 120, find the 15th term.​

Sagot :

Answer:

345.

Explanation:

Sum of n terms = n/2[2a1 + (n-1)d]

So 400 = 10/2(2a1 + 9d) and

120 = 3(2a1 + 5d)  so we have the system:

400 = 10a1 + 45d ......... A

120  = 6a1 + 15d    ..........B         multiply this by 3:

360  = 18a1 + 45D     Subtract this from equation A:

40 = -8a1

a1 = -5

So plugging this value into B:

d =  (120 - 6*-5) / / 6

= 150/6 = 25.

15th term = a1 + (n - 1)d

= -5 + (15-1)25

=  345.

We hope you found what you were looking for. Feel free to revisit us for more answers and updated information. We appreciate your time. Please revisit us for more reliable answers to any questions you may have. Westonci.ca is committed to providing accurate answers. Come back soon for more trustworthy information.