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Worked Examples · Example 22

Q.Find the cost of

(i) ₹7200, 8% stock at 90
(ii) ₹4500, 8.5% stock at 4 premium
(iii) ₹6400, 10% stock at 15 discount
Andaman Nicobar CbseNCERTSubjective· 5mImportance★★★★★est
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✓ Free question

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

Tip

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.

Watch out

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 FF and market price MM per ₹100:

Cost=F×M100\text{Cost} = F \times \frac{M}{100}


✓Final answer

The costs are: (i) ₹6480,

(ii) ₹4680,

(iii) ₹5440.

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