The true discount on ₹ 2562 due 4 months hence is ₹ 122. The rate percent is
Aptitude
True Discount
Difficulty: Medium
Choose an option
-
A12%
-
B$13\frac{1}{3}$%
-
C15%
-
D14%
Answer
Correct Answer: 15%
Explanation
### Concept & True Discount Logic
The true discount is the simple interest on the Present Worth. We can find the Present Worth by subtracting the true discount from the total amount due.
$$ \text{PW} = \text{Amount} - \text{TD} $$
$$ R = \frac{100 \times \text{TD}}{\text{PW} \times T} $$
### Step-by-Step Solution
- Given Amount = ₹ 2562
- True Discount (TD) = ₹ 122
- Time (T) = 4 months = $\frac{4}{12}$ years = $\frac{1}{3}$ year
- Find the Present Worth (PW):
$$ \text{PW} = 2562 - 122 = 2440 $$
- Now substitute PW, TD, and T into the rate formula:
$$ R = \frac{100 \times 122}{2440 \times (\frac{1}{3})} $$
$$ R = \frac{12200}{\frac{2440}{3}} = \frac{12200 \times 3}{2440} $$
$$ R = 5 \times 3 = 15\% $$
### Exam Strategy & Shortcut
Instead of writing complex fractions, observe that 122 is exactly 1/20th (or 5%) of 2440. If the interest for 1/3 of a year is 5%, the interest for a full year is $5\% \times 3 = 15\%$.
### Common Pitfall
Forgetting to convert months into years. Using T = 4 instead of T = 1/3 will yield a drastically incorrect, tiny rate percentage.
### Final Answer
Therefore, the correct answer is **15%**.