In an A.P if the 12th term is -13 and the sum of first four terms is 24 what is the sum of the first 10 terms.
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term12=-13
a+(n-1)d = -13
a+11d= -13 equation 1
Sum of 4 term= 24
n/2 (2a + ( n-1)d)= 24
2(2a+3d)= 24
2a+3d=12 equation 2
Equation 1 and 2
a+11d=-13
2a+3d=12
=> 2a+22d=-26
2a+3d=12
=> -19d=38
d=-2
a=9
Sum of 10 term = n/2(2a+(n-1) d )
=5(18+(9)-2)
=0
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