Q.Find the cost of
The cost of a stock is the market price paid for it, not its face value. For (i) ₹7200 stock at 90 costs ₹6480; for (ii) ₹4500 stock at 4 premium costs ₹4680; for (iii) ₹6400 stock at 10% discount costs ₹5440.
The Core Idea: Face Value vs. Market Price
When you buy stock, you're buying a certificate that promises to pay you a fixed percentage of its face value (the printed amount on the certificate) as interest. But you don't pay the face value — you pay the market price, which is quoted per ₹100 of face value.
- "At 90" means ₹90 market price for every ₹100 face value.
- "At 4 premium" means ₹100 + ₹4 = ₹104 market price per ₹100 face value.
- "At 15 discount" means ₹100 − ₹15 = ₹85 market price per ₹100 face value.
The cost of the stock is simply: (Face value of stock) × (Market price per ₹100) ÷ 100.
Step-by-Step Solutions
1. ₹7200, 8% stock at 90
Reasoning: The stock has a face value of ₹7200. The market price is 90, meaning ₹90 for every ₹100 of face value. So the cost is a direct proportion.
Cost = Face value × (Market price / 100)
Cost = ₹7200 × (90 / 100) = ₹7200 × 0.9 = ₹6480
You can think of "at 90" as a 10% discount on face value. So cost = 90% of face value. Quick mental check: 10% of 7200 is 720, so 90% is 7200 − 720 = 6480.
2. ₹4500, 8.5% stock at 4 premium
Reasoning: "At 4 premium" means the market price is ₹100 + ₹4 = ₹104 per ₹100 face value. The face value is ₹4500.
Cost = ₹4500 × (104 / 100) = ₹4500 × 1.04
Let's compute: 4500 × 1 = 4500, and 4500 × 0.04 = 180. So total = 4500 + 180 = ₹4680.
A common mistake is to treat "premium" as an extra amount added to the total face value. It's not — it's a per-₹100 rate. Always convert to a price per ₹100 first.
3. ₹6400, 10% stock at 15 discount
Reasoning: "At 15 discount" means the market price is ₹100 − ₹15 = ₹85 per ₹100 face value. The face value is ₹6400.
Cost = ₹6400 × (85 / 100) = ₹6400 × 0.85
Compute: 6400 × 0.8 = 5120, and 6400 × 0.05 = 320. So total = 5120 + 320 = ₹5440.
For any stock with face value and market price per ₹100:
The costs are: (i) ₹6480,
(ii) ₹4680,
(iii) ₹5440.
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