Question

The amount of Rs. $5000$% is put into three investments of $6$%, $7$% and $8$% per annum respectively. The total annual income from these investments is Rs. $360$. If the total annual income from the first two investments is Rs. $40$ more than the income from the third, find the amount in each investment by matrix adjoint method

Answer 1

Let the amounts invested be $P_1,P_2,P_3;P_1+P_2+P_3=5000$ and ;

$6P_1+7P_2=4000+8P_3;6P_1+7P_2+8P_3=36000⟹P_3=2000,P_2=2000,P_1=1000$