All MCQs

A 20% profit gives a selling price of Rs. 960.
Since this is 80% of marked price, marked price = 960/0.8 = Rs. 1,200.

A's capital-time is 2 × 6 + 4 × 6 = 36 units.
B's is 3 × 12 = 36 units, so profits are equal.

Capital-time products are 40,000 × 12 and 60,000 × 8.
Both equal 480,000, so the ratio is 1:1.

Profit is shared in the ratio of investments, 3:5.
B receives 5/8 of Rs. 16,000 = Rs. 10,000.

One-year compound amount is principal plus 12% interest.
Thus, 20,000 × 1.12 = Rs. 22,400.

Doubling means interest equal to the principal is earned in 8 years.
Tripling requires interest equal to twice the principal, so it takes 16 years.

For two years, the difference is P(r/100)².
So 10,000 × 0.1² = Rs. 100.

The amount is 8,000 × 1.05² = Rs. 8,820.
Subtracting the principal gives compound interest of Rs. 820.

Compound amount is P(1 + r)².
Thus, 10,000 × 1.1² = Rs. 12,100.

Rate = SI × 100 ÷ (P × T).
Thus, 800 × 100 ÷ (4,000 × 5) = 4%.

Using SI = PRT/100, 900 = P × 6 × 3/100.
Solving gives P = Rs. 5,000.

Simple interest is PRT/100.
So 5,000 × 8 × 3 ÷ 100 = Rs. 1,200.