Let the original price be x. Selling Price = x - 20% of x = 120. Thus, 0.8x = 120, so x = 150.

Let the original price be x. Then, 120 = x - 20% of x => 120 = x - 0.2x => 120 = 0.8x => x = 150.

Let the marked price be x. Then, Selling Price = x - (20% of x) = 240 => 0.8x = 240 => x = 300.

Let the original price be x. Selling Price = x - 20% of x = 0.8x. Thus, 0.8x = 240, so x = 300.

Let the marked price be x. Selling Price = Marked Price - Discount = x - 0.2x = 0.8x. Thus, 0.8x = 240, so x = 300.

Let the marked price be x. After a 20% discount, the selling price is x - (0.20 * x) = 0.80x. Setting this equal to $80 gives 0.80x = $80, so x = $80 / 0.80 = $100.

Let the cost price be x. Selling price = cost price - loss = x - (0.10 * x) = 0.90x. Setting this equal to $90 gives 0.90x = $90, so x = $100.

25% of 40 liters is 0.25 * 40 = 10 liters of acid.

25% of 40 liters = 0.25 * 40 = 10 liters of sugar.

Total parts = 3 + 5 = 8. Ratio of A = 3:8.

Concentration = (30% + 70%) / 2 = 50%.

Total solute = (0.2 * 5) + (0.1 * 15) = 1 + 1.5 = 2.5 liters. Total volume = 5 + 15 = 20 liters. Concentration = (2.5/20) * 100 = 12.5%.

The volume of a sphere is given by V = (4/3)πr³. Setting (4/3)πr³ = 288π, we find r³ = 216, thus r = 6 cm.

Let the marked price be x. After a 20% discount, the selling price is x - (0.20 * x) = 0.80x. Setting this equal to $80 gives 0.80x = $80, so x = $100.

Correct answers = 80% of 50 = 0.8 * 50 = 40.

Percentage correct = (90 / 120) * 100 = 75%.

Incorrect answers = 120 - 90 = 30. Percentage incorrect = (30/120) * 100 = 25%.

The number of questions answered correctly is 90% of 200, which is 180. Therefore, the number of questions answered incorrectly is 200 - 180 = 20.

If 90% were answered correctly, then 10% were answered incorrectly. Therefore, the number of incorrect answers is 10% of 200, which is 20.

The number of ways to choose 2 subjects from 5 is 5C2 = 10.

The number of ways to choose 2 subjects from 5 is given by 5C2 = 10.

Average percentage = (75% + 85%) / 2 = 80%.

Percentage score = (90/120) * 100 = 75%.

The formula for simple interest is A = P(1 + rt). If the amount doubles, A = 2P. Therefore, 2P = P(1 + r*5). Simplifying gives r = 0.1 or 10%.

The formula for simple interest is A = P(1 + rt). If the amount doubles, A = 2P. Therefore, 2P = P(1 + r*5). Simplifying gives r = 0.1 or 10%.

Using the formula for simple interest, SI = PRT, where SI = Principal, R = Rate, and T = Time. If the principal doubles in 5 years, then SI = P. Therefore, P = PRT implies R = 1/5 = 20%. Hence, the rate of interest is 10%.

Using the formula for simple interest, we know that the interest earned is equal to the principal. Therefore, if the principal doubles in 5 years, the rate of interest can be calculated as (100 * Interest) / (Principal * Time) = (100 * Principal) / (Principal * 5) = 20%. Thus, the rate of interest is 20%.

Using the rule of 72, we estimate the time to double as 72/12 = 6 years.

Using A = P(1 + r)^t, A = 1000(1 + 0.06)^5 = 1000 * 1.338225 = 1338.23.

Using the formula A = P(1 + rt), we have 3P = P(1 + 0.06t). Solving gives t = 20 years.