Question

どんちっちｱｼﾞ('-' 鯵)зIB生@⚡︎な病民

この問題解説お願いします🙇‍♀
答えは右です。

9 Jim issaving money to buy a car He puts 620 in thc bank

jn the first weck. then 625 in the second week then 630
the third week。 and so on.
s How much will Jim put into he bank in the 10h
week?
5 How much money will Jim have saved in total aer
20 wecks?

Thc amangcment of numbens alongside is called a 3 x 3 magie
square. The numbers from 1 to 9 are placed so that the numbers
jm cach row column and main diagonal all add up to the same
number known as the magic constant Fora3x3 magic square。
the magic constant is 15.
An xn magic squarc contains the numbcrs from 1 to 2.

き Find. in tems of thc magic constant for an nx magic

Square」
も Check that your fommula is comect for nニ8.
で Find the magic constant for an 8 x 8 magic square.

b 840

9 a 665     b 1350

4 (2 十1)  b 3(32二1) 3x10
き             ーー 2

EXERCISE 16F1 還還EE

ai

10             15 / < 260

Answer 1

ケスト

9は等差数列

どんちっちｱｼﾞ('-' 鯵)зIB生@⚡︎な病民

すみません🙏🙏🙏
もっと詳しくお願いします🙇‍♀️

ケスト

一週間目20ドル
二週間目25ドル
三週間目30ドル

ってことは5ドルずつ増えてる
初項20,公差5の(項数n(n週間目))の等差数列と捉えられる
一般項はan=20+(n-1)5=5n+15
n=10のときa10=65

n=20のときa20=115
S20=(1/2)×20×(20+115)=1350

ケスト

ドルじゃないか

どんちっちｱｼﾞ('-' 鯵)зIB生@⚡︎な病民

ありがとうございます！
10番もお願いします🙇‍♀️