Question

Two APs have the same c.d .if the first terms of these APs be 9 and 4 respectively ,find the difference between the sums of their first 40 terms.​

Answer 1

Answer:

200

Step-by-step explanation:

 GIVEN COMMON DIFFERENCE OF BOTH APS IS SAME

          LET THE C.D BE d

          FIRST TERM OF AP1  =   9

          SUM UPTO FORTY TERMS = (40/2)(18 + 39d)=20(18+39d)

          FIRST TERM OF AP2  = 4          

          SUM UPTO 40 TERMS = (40/2)(8+39d)  = 20(8+39d)

            DIFFERENCE BETWEEN SUM = 20(10)

           DIFFERENCE = 200

       SUM UPTO N TERMS = (N/2){2a+(n-1)d}

         HOPE IT HELPS YOU