Problem Solving (Show your calculations/steps)

The percentage profit selling a product for TK 1920 is equal to the percentage loss incurred by selling the same product for TK. 1280. What price should the product be sold to make 25% profit. 

Solve the following mathematical problems:

Nipu sold 100 pens of which 50 are red and 50 are black, at tk. 48 per pen. He made a profit of 20% on the blank pens and made a loss of 20% red pens. What was the net gai or net loss on this sale in Tk?

Solve the following mathematical problems:

A trader purchases blue paint and yellow paint at a price of Tk. 110 and Tk. 100 per liter respectively . He mixes blue and yellow paint at a ratio of 1:21 to make a certain paint of green color. He sells the green pair at a price of Tk. 120 per liter. If the trader makes a profit of Tk. 2000, how much yellow paint (in kg) did he use in the mixture?

Solve the following mathematical problems:

In a class of 25 students , 10 have less than 6 marbles, 10 have more than 7 marbles and 4 have more than 8 marbles. How many students have more than 5 marbles but less than 9 Marbles?

Problem Solving (Show your calculations/steps)

The sum of two digits of a number is 16. If the digits of this number are interchanged, then the new number that we get is 18 greater than the original number. What is the original two-digit number?

Solve the following mathematical problems:

A ship with a faulty engine sailed for only 7 hours over a period of 2 days and covered a distance of 59 kms. It average speed on the first day was 5 km per hour slower than that on the second day. But it sailed 3 hours longer on the first day than that on the second day. What was its average speed on the second day?