A woman invests $3000 in government bonds for 5 years at 7% simple interest. a)Calculate the total interest she receives for 5 years.
b) Calculate the sum that must be invested in bonds to obtain a total interest of $3500 in 5 years.

help with b ??

7000 dollar, I guess.

Step-by-step explanation:

As we know the equation of simple interest is : I=Pnr

where I-interest

           P-principal or in this case the sum

           n- number of years

           r- rate perchantage

       as it asks for the sum, it should be:

         P= I/nr

           =3500 / 0.007 x 5 ( 7%= 0.007)

           = 10000

as she already invested 3000, so remains = (10000-3000)

                                                                       = 7000 dollar