Percentages

Let John's income be j and Peter's income be p. Then, j = p + p × 33.33% = p + p × 100⁄3 % = p + p × 1/3 = 4p/3 ⇒ p = 3j/4 = (4 - 1)j/4 = j - j/4 = j - j × 1/4 = j - j × 100⁄4 % = j - j × 25%. Therefore, Peter's earning is less than John's earning by 25%.

Let her old salary be Rs 100. Then, her new salary = 100 - 10 = Rs 90. So, to gain her old salary, her new salary must be increased by Rs 10. Therefore, the required percentage = (10⁄90) × 100% = 100/9 %.

Let the price of sugar be Rs 100 and monthly sales be 100 units. Then, total revenue = 100 × 100 = Rs 10000. And, new revenue = 90 × 130 = Rs 11700. Increase in revenue = 11700 - 10000 = Rs 1700. Hence, percentage increase in revenue = (1700/10000) × 100% = 17%.

Let Jack's original salary be Rs 100. Then, his expenditure = Rs 75, his savings = Rs 25. Now, his new salary = Rs 120. So, new expenditure = (110/100) × 75 = Rs 165/2, new savings = 120 - 165/2 = Rs 75/2. Increase in savings = 75/2 - 25 = Rs 25/2. Therefore, percentage increase in savings = (25/2)/25 × 100% = 50%.

Original Price of the item = 25 + 5 = Rs 30. Hence, the required percentage = (5/30) × 100% = 50/3 %.

Rebate received by Barack = 6% of Rs 6650 = 6/100 × 6650 = 3/5 × 665 = Rs 399. Sales Tax paid by Barack = 10% of Rs (6650-399) = 10% of Rs 6251 = Rs 625.10. Therefore, Barack's total expenditure = Rs (6251 + 625.10) = Rs 6876.10.

Let Felix's monthly salary be Rs x. Then, (100 - 66.66)% of x = Rs 1200 ⇒ 33.33 % of x = Rs 1200 ⇒ x/3 = Rs 1200 ⇒ x = Rs 3600. Therefore, his monthly expenditure = 3600 - 1200 = Rs 2400.

Let Robert's score be x. Then, Jack's score = x+9. Now, x+9 = 56% of [(x+9) + x] ⇒ x+9 = 14/25 × (2x + 9) ⇒ 25 × (x+9) = 14 × (2x+9) ⇒ 25x + 225 = 28x + 126 ⇒ 3x = 99 ⇒ x = 33. Therefore, Robert scored 33 marks and Jack scored 42 marks.

10000*20/100 = 2000

[10000-(10000*20/100)]*15/100 = 1200