a boy is excited about his birthday which is approaching. He collects 1 leaf on the first day of the month to 2 leaves on the second day and 3 leaves on the third day of the month and so on. On his birthday he finds that he is collected 210 leaves in all. on which day of the month is this birthday.
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Answered by
9
here sum = 210
first term is 1
common difference = 1
Sum of AP = n/2(2a+(n-1)d)
n/2(2+n-1)= 210
n²+n = 420
n²+n-420=0
n²+21n-20n-420=0
n(n+21) -20(n+21)=0
(n+21) ( n-20) =0
either n = -21 or n =20
since n= -21 not possible so
answer is n= 20
boy will have his b'day on 20
first term is 1
common difference = 1
Sum of AP = n/2(2a+(n-1)d)
n/2(2+n-1)= 210
n²+n = 420
n²+n-420=0
n²+21n-20n-420=0
n(n+21) -20(n+21)=0
(n+21) ( n-20) =0
either n = -21 or n =20
since n= -21 not possible so
answer is n= 20
boy will have his b'day on 20
Answered by
7
Hope it helps u......☺
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