Sita has $100 in her piggy bank. How much will she have in her bank 20 weeks from now if she puts $1 in the bank next week, $2 two weeks from now, $3 three weeks from now, and continues to increase the amount that she puts in by $1 each week? Choose the most appropriate option:  A) 300  B) 310  C) 320  D) 330  E) 340
The dollar deposits are in an A.P.   1,2,3,4...20 with common difference 1   Sum of the terms is n(n+1) / 2   i.e 20 * (20+1) /2   = 20 * 21/2= 
<gadget id="calculator">20 * 21/2</gadget>
<output>210</output>
210   Total deposit therefore with Chiu-Lihas is 100 + 210= 
<gadget id="calculator">100 + 210</gadget>
<output>310</output>
310$
<result>B</result>
Sita has $100 in her piggy bank. How much will she have in her bank 20 weeks from now if she puts $1 in the bank next week, $2 two weeks from now, $3 three weeks from now, and continues to increase the amount that she puts in by $1 each week?