Formula help please

Hi My son has a table for maths which he needs to work out a formula for. He can see the link but can't work out how to write the formula. Maths is not my strong point! Sorry the columns are all squashed to the left. From what he sees column 2 = day x 100 and column 3 = column 2 plus the previous days column 3. I'm sure there's an easy formula!


Day Prize money on each day Total amount
1 $100 $100
2 $200 $300
3 $300 $600
4 $400 $1,000
5 $500 $1,500
6 $600 $2,100
7 $700 $2,800
8 $800 $3,600
9 $900 $4,500
10 $1,000 $5,500
11 $1,100 $6,600
12 $1,200 $7,800
13 $1,300 $9,100
14 $1,400 $10,500
15 $1,500 $12,000
16 $1,600 $13,600
17 $1,700 $15,300
18 $1,800 $17,100
19 $1,900 $19,000
20 $2,000 $21,000
21 $2,100 $23,100