NET Mathematics MCQs

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.

The difference between C and A is 2 ratio parts, equal to Rs. 600.
One part is Rs. 300, so 12 parts total Rs. 3,600.

Initially, milk is 42 liters and water is 18 liters.
For a 7:5 ratio with 42 liters milk, water must be 30 liters, so add 12.

Let the numbers be 5k and 8k; then (5k + 9)/(8k + 9) = 2/3.
Solving gives k = 9, so the smaller number is 45.

Profit equals selling price minus cost price.
Thus, 920 - 800 = Rs. 120.

A 10% loss on Rs. 1,200 is Rs. 120.
Subtracting gives a selling price of Rs. 1,080.

The selling price is 125% of the cost price.
Thus, cost price = 1,500 ÷ 1.25 = Rs. 1,200.

The discount is 15% of Rs. 2,000, which is Rs. 300.
The sale price is Rs. 2,000 - Rs. 300 = Rs. 1,700.

After a 10% discount, 90% remains; after another 20%, 80% of that remains.
The final price is 72%, so the total discount is 28%.

Let cost be 100; marked price is 125 and sale price is 90% of 125 = 112.5.
The profit is 12.5 on a cost of 100.

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

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