Arithmetic and Debu: Discussion on Important Mathematical Questions

Objective

• Achieve 80% hit rate and 90% accuracy
• Solution in minimum time
• If it's a level 1 question, it should be solved in 32-45 seconds, and medium to hard questions in 1-1.5 minutes.

Methodology

• Everyone should focus on being strong in percentages and arithmetics.
• We have been doing arithmetic since childhood, but due to struggle, it seems challenging.

Important Questions

Profit and Loss

• Under the profit and loss topic:
  • Calculate profit and discount between count price, selling price, mark price.
  • Example: If there's a 20% profit and cost price is 100, it will be 120.
• Margin: Often applied in companies.
  • For example, how to calculate 50% markup and 20% discount.
• Successive changes: Simple formula: A + B + A.B/100.
  • Change perspective to multiply and calculate percentages.

Interest

• Basic concept of simple interest and compound interest.
  • Example: If the principal amount is 1000 and the rate is 10%, calculate the time for simple interest.
• The more you calculate interest in installments, the more you earn. Core principles ⟿ Consider the percentage with N terms.
  • Example: If you want to double 1000 rupees with compound interest, how long will it take?

Time Speed Distance

• Distance = Speed X Time.
  • Example: If an object is at x speed, what will be its distance?
• Use of reciprocal:
  • If speed is constant, time is constant. It can be considered in time distance questions.
  • Simple example: Covered 100 meters distance in 32 seconds.
• Escalator Question: Distance will always be there, mention the speed.
  • The height concept is the same, as given in Uncle Sasta Washree's example.

Mixture and Alligation

• Simple average mixture and application of alligation.
  • Mixing concentrations and finding average concentration like mixing 30% and 60% to find the percentage.
• Replacement formula: (Original concentration)x(1-fake)/ (total -1/number of times) is completed.
  • Example: Mixing 10 liters of milk and 10 liters of water.

Work and Time

• Solution through LCM method: or solve days using LCM. Also, calculate using one day work method.
  • Example: One task can be completed in 10 days and another in 20 days. How many days together to solve it?

The Challenge

• Revise respective time, speed, distance, work and time individual percentages, and return on investment.
  • Rate count, total work, and allegation.
• There should be a balance of personal experience and effort in the questions.