Question

The first term of An Ap is -5 and last term is 45. sum of the terms of the ap is I20. find the number of terms and common difference

Answer 1

number of terms is 6 and C.D is 10.
equate Sn =n/2(a+l) to 120 u get n=6.
put n=6 in a+(n-1)D u get D=10