Problem in Profit and Loss

Two merchants sell, each an article for Rs.1000. If Merchant A computes his profit on cost price, while Merchant B computes his profit on selling price, they end up making profits of 25% respectively.
By how much is the profit made by Merchant B greater than that of Merchant A?
(1) Rs.66.67
(2) Rs. 50
(3) Rs.125
(4) Rs.200

Can some one help me out in solving this problem?

Profit loss problem

A stockist wants to make profit by selling grains. Which of the following would maximize his profit?
I. Sell grains at 20% profit.
II. Use 800 g of weight instead of 1 kg.
III. Mix 20% impurities in grains and sell it at cost price.
IV. Increase the price by 10% and reduce weights by 10%

2)I or III
3)II, III and IV
4)Profits are same Please help me out with this problem,do explain thanks in advance

Problem on simple and compound Interest

Hello, Can some one help me in solving this problem.

Ravi invests a two equal amounts in two different schemes run by a bank. After 2 years, he gets Rs.700 as the simple interest in the first scheme, while in the second scheme he gets Rs.749 as the compound interest. What is the total amount he invested in both the schemes?

Note: The solution for this problem is given based on the concept: Compound Interest for 2 years - Simple Interest for 2 years = Interest earned on Simple Interest of 1st year during the course of second year.

Is there any other way to solve this problem?

Thanks in advance.