SOLUTION: I need to see how to solve this word problem: A boy was offered a bonus if he sold 100 subscriptions to a magazine. Each day he sold 3 subscriptions more than he had on the pre

Question 430098: I need to see how to solve this word problem:
A boy was offered a bonus if he sold 100 subscriptions to a magazine. Each day he sold 3 subscriptions more than he had on the previous day, and on the 8th day he reached his 100 quota. How many subscriptions did he sell each day?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A boy was offered a bonus if he sold 100 subscriptions to a magazine.
Each day he sold 3 subscriptions more than he had on the previous day, and on the 8th day he reached his 100 quota.
How many subscriptions did he sell each day?
-----
Arithmetic Sequence with common difference = 3
and S(8) = 100
----
Solve:
S(8) = (8/2)(1st + last)
100 = 4(1st + last)
1st + last = 25
----
a(n) = 1st+(n-1)d
last = a(8) = 1st+7*3
---
Solve:
1st+ [1st+21] = 25
2*1st + 21 = 25
1st = 2
----
1st day: 2
2nd: 5
3rd: 8
4th: 11
5th: 14
6th: 17
7th: 20
8th: 23
---
Sum = 100
=================
Cheers,
Stan H.

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