# A person invests $5000 in treasury notes and bonds. The notes pay 8% annual interest and the bonds pay 10% annual interest. If the annual in- come is$480, how much is invested in treasury notes?

Investment in treasury notes is $1000. #### Explanation: Let the money invested in treasury notes be $x. Annual income on it at 8% per annum for a year will be $\frac{8}{100} \times x$.
Then money invested in bonds at 10% would be $(5000-x) and annual income on it for a year will be $\frac{10}{100} \times \left(5000 - x\right)$. As total yield is $480$, we have $\frac{8 x}{100} + \frac{10 \left(5000 - x\right)}{100} = 480$- multiplying both sides by $100$or $8 x + 10 \left(5000 - x\right) = 48000$or $8 x + 50000 - 10 x = 48000$or $- 2 x = 48000 - 50000 = - 2000$i.e. $x = - \frac{2000}{-} 2 = 1000$Hence, investment in treasury notes is $1000.