Home>Mental Math: Doubling and Halving
Lesson by Mike McGarry
Magoosh Expert

Summary
The content focuses on a mental math trick known as doubling and halving, which simplifies multiplication tasks by adjusting the factors in a way that the overall product remains unchanged. This technique is particularly useful for GMAT test-takers aiming to enhance their quantitative problem-solving efficiency.
• Doubling and halving leverages the associative property of multiplication to simplify calculations by doubling one factor and halving the other without changing the product.
• This method is especially advantageous when one of the factors ends in 5 or 50, making it easier to multiply by converting it into a round number.
• Practical examples demonstrate how to apply this trick to perform seemingly complex multiplications quickly in one's head, highlighting its utility in saving time during the GMAT Quant section.
• The technique can be applied successively, particularly when dealing with factors like 25 or multiples thereof, to further simplify calculations.
• Regular practice of this trick can significantly improve mental math skills, making it a valuable strategy for test-takers.
Chapters
00:00
Introduction to Doubling and Halving
00:16
Applying the Trick to Simplify Multiplication
02:06
When to Use Doubling and Halving
02:53
Practical Examples and Practice Problems