Question

Stonewall receives ¢250 per year in simple interest from an amount of money he invested in
ADB, Barclays and GCB. Suppose ADB pays an interest of 2%, Barclays pays an interest of
4% and GCB pays an interest of 5% per annum and an amount of ¢350 more was invested in
Barclays than the amount invested in ADB and GCB combined. Also, the amount invested in
Barclays is 2 times the amount invested in GCB.
a) Write down the three linear equations and represent them in the matrix form �� = �.
b) Find the amount of money Stonewall invested in ADB, Barclays and GCB using Matrix
Inversion

Answer 1

The denominator of a fraction is one more than twice the numerator. If the sum of the fraction and its reciprocal is 22116, find the fraction.

Then Denominator=2x+1

Fraction =2x+1x

Reciprocal of the fraction =x2x+1

It is given that the sum fo the fraction and its reciprocal is 22116

∴2x+1x+x2x+1=22116

⇒x(2x+1)x2+(2x+1)2=2158⇒2x2+x5x2+4x+1=2158

⇒21(5x2+4x+1)=58(2x2+x)⇒105x2+84x+21=116x

⇒11x2−26x−21=0⇒11x2−33x+7x−21=0⇒11x(x−3)+7(x−3)=0

⇒(11x+7)(x−3)=0⇒x=3,−117

∵ x can not be a negative 

⇒x=3

Time = 15 min = 15/60 = 0.25

Length of bridge = 1250 m

Hope this helps you.