Question

The first term of AP is5, the last term is 45 and the sum is 400 find the number of terms and the common differences

Answer 1

Answer:

Step-by-step explanation:

Given:

a=5

l=45

Sn=400

Ans:

             Sn=n/2(a+l)

         400  =n/2(5+45)

        400   =n/2(50)

       400    = n(25)

 400/25    = n

            16   =n

             n=16

              therefore:

              an=a+(n-1)d

              45=5+(17)d

        45-5  =(17)d

            40 = (17)d

           40/17=d

   

               d=40/17