Question 599891
let's assume additional sum invested in government securities is $ x.

Total investment                  = $ x+10000
Interest on total investment      = $ (x+10000) * 4.5/100
Interest on corporate bond        = $ 10000 * 7/100       = $ 700
                                  
Interest on government securities = $ x * 4/100


Since the interest from both sources should add up to total interest earned
we get the following equation which we proceed to solve

 
        (x+10000) * 4.5/100 = 700 + x * 4/100


Multiplying both sides by 100 we have
        (x+10000) * 4.5     = 70000 + x *4
i.e.     4.5x + 45000       = 70000 + 4x
i.e.     4.5x - 4x          = 70000 - 45000
i.e.     0.5x               = 25000
i.e.        x               = 25000 * 2


Hence amount to be invested in government securities is $ 50,000.