What sum will amount to Rs. 7000 in 5 years at $${\text{3}}\frac{1}{3}$$ % simple interest ?
a) Rs. 6300
b) Rs. 6500
c) Rs. 6000
d) Rs. 5000

Answer: c
Explanation:
$$\eqalign{ & {\text{Amount Rs 7000}} \cr & {\text{Total interest in 5 years}} \cr & {\text{ = 5}} \times \frac{{10}}{3}\% = \frac{{50}}{3}\% = \frac{1}{6} \cr} $$

Principal	Amount
6	(6 + 1)
↓ × 1000	↓ × 1000
6000	7000

Required principal = Rs. 6000