Ram has $100 in her piggy bank. How much will she have in her bank 25 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 $1 each week?  Choose one.
A) 400  B) 415  C) 425  D) 435  E) 445
The dollar deposits are in an A.P.   1,2,3,4...25 with common difference 1   Sum of the terms is n(n+1) / 2   i.e 25* (25+1) /2   = 25* 26/2= 
<gadget id="calculator">25* 26/2</gadget>
<output>325</output>
325   Total deposit therefore with 425hiu-Lihas is 100 + 325= 
<gadget id="calculator">100 + 325</gadget>
<output>425</output>
425$
<result>C</result>
Ram has $100 in her piggy bank. How much will she have in her bank 25 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?