Question

if 12 term of am ap is -13 and the sum of first four term is 24 what is the sum of 10 term?
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Answer 1

Step-by-step explanation:

given: 12th term: t12= -13

we know that: t12= a+11d

where, a is first term and d is common difference....

so, a+11d= -13.........(1)

sum of first four terms= 24

we know sum formula: s= n(2a+(n-1)d)/2

where n= no. of terms

by substituting values in sum formula....we have..

24 = 4(2a+3d)/2

so, 2a+3d = 12.......(2)

by solving equation (1) amd (2) we get values as....

a= 9, d= -2

so, sum to ten terms formula: s= 10(2a+9d)/2

s= 10(18-18)/2

so, s= 0

therefore, sum of ten terms = 0

hope it helps you....