A lends Rs. 2500 to B and a certain sum to C at the same time at 7% p.a. simple interest. If after 4 years, A altogether receives Rs. 1120 as interest from B and C, then the sum lent to C is :

Let the sum lent to C be Rs. x.
Then,
$$\eqalign{ & \left( {\frac{{2500 \times 7 \times 4}}{{100}}} \right) + \left( {\frac{{x \times 7 \times 4}}{{100}}} \right) = 1120 \cr & \Rightarrow \frac{{7x}}{{25}} = \left( {1120 - 700} \right) \cr & \Rightarrow x = \left( {\frac{{420 \times 25}}{7}} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\, = 1500. \cr} $$