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Mental Math: Doubling and Halving

The content focuses on a mental math trick of doubling and halving to simplify multiplication problems, particularly useful for the GRE exam's Quant section.
  • Doubling one factor and halving the other in a multiplication problem does not change the product, making calculations easier.
  • This trick is especially useful when one of the factors ends in 5 or 50, as doubling it results in a round number, simplifying the multiplication.
  • Practicing this trick can significantly speed up calculations, saving valuable time during the exam.
  • The trick can be applied multiple times in succession for factors like 25 or multiples of 25, further simplifying calculations.
  • Examples and practice problems demonstrate how to apply this trick effectively, highlighting its utility in making seemingly difficult calculations manageable.
Introduction to Doubling and Halving
Applying the Trick
When to Use the Trick
Practical Examples
Summary and Importance