A farmer, have 2100 ducks and he sell 10 of his ducks at the end of the first week, 20 at the end of second week and so on, selling each week 10 more than previous week. After how many weeks will he have to sold all of his ducks??

Question

anonymous · Answer

my ans has no real value... pls help me to slove...  the ans should be real.. becoz week cant be imaginary num...

king · Answer

20

anonymous · Answer

ya is 20... but how you get the ans??

king · Answer

i added one by one 
tryin to figure out how to do algebraically

anonymous · Answer

i use the arithmetic progression formula to slove...
Sn=(n/2)(2a+(n-1)d
where a is the first term, d is the difference, n is nth term

anonymous · Answer

20 weeks. I started with 2100 and the subtracted 10. The subtracted 10 from that answer and so on till I had 0 left. then I counted how many times it took me to get to 0. I have no idea how to solve it algebraicly.

anonymous · Answer

.... haha.... careless mistake.. XD i get the ans already...

anonymous · Answer

ok lol