A ruby stone was bought for Rs 1600 at Jaipur. A sum of Rs2400 was spent on making a ring with the ruby stone. It was advertised for sale at Bombay for Rs 7800. If a discount of 10% was given, then the % profit made was.
एक रूबि पत्थर जयपुर में Rs1600 में खरीदा गया। रूबि पत्थर के साथ अंगूठी बनाने पर Rs 24000 व्यय किए गए। बंबई में उसे Rs 7800 में बिक्री के लिए विज्ञापित किया गया। यदि 10% की छूट दी गई हो, तो अर्जित % लाभ है| Options are (a) 0.55 (b) `68.5%` (c) `75.5%` (d) `80%`.

Options

A. 0.55
B. `68.5%`
C. `75.5%`
D. `80%`

Explanation

To solve the problem, we need to calculate the total cost price (CP), the selling price (SP) after the discount, and then find the percentage profit.

### Step-by-Step Solution:

1. **Calculate the Total Cost Price (CP)**:
- The cost price of the ruby stone = Rs 1600
- The cost of making the ring = Rs 2400
- Total CP = Cost of ruby stone + Cost of making the ring
\[ \text{Total CP} = 1600 + 2400 = 4000 \]

2. **Calculate the Selling Price (SP) after Discount**:
- The marked price (MP) of the ring = Rs 7800
- Discount = 10% of MP
\[ \text{Discount} = \frac{10}{100} \times 7800 = 780 \]
- Selling Price (SP) = Marked Price - Discount
\[ \text{SP} = 7800 - 780 = 7020 \]

3. **Calculate the Profit**:
- Profit = Selling Price - Cost Price
\[ \text{Profit} = 7020 - 4000 = 3020 \]

4. **Calculate the Percentage Profit**:
- Percentage Profit = \(\left(\frac{\text{Profit}}{\text{CP}}\right) \times 100\)
\[ \text{Percentage Profit} = \left(\frac{3020}{4000}\right) \times 100 = 75.5\% \]

### Final Answer:
The percentage profit made is **75.5%**.