Fast math  Vedic Mental Math Tricks  Multiplication 07  Don't Memorise  Summary and Q&A
TL;DR
Learn how to multiply numbers that are close to multiples of 10 using the base, deviation, sum, product, and multiplying factor method.
Key Insights
 😚 Multiplying numbers close to multiples of 10 involves finding the base, the deviations, the sum, the product, and the multiplying factor.
 😚 The base is a multiple of a power of 10 that the numbers are close to.
 ⚾ The deviations represent the difference between each number and the base.
 ↔️ The sum is the result of adding the deviations on the left, and the product is the result of multiplying the deviations on the right.
 The multiplying factor is used to multiply the number on the left before adding the righthand result.
Transcript
before we move on to big numbers try multiplying 61 with 64 we have seen examples like 98 * 97 where both numbers were below the base 102 * 103 where both numbers were above the base and 13 * 998 where one was above and the other below the base but in all cases the base was a power of 10 like 10 100 1,000 and so on but here the numbers are not clos... Read More
Questions & Answers
Q: How do you determine the base when multiplying numbers that are not close to a power of 10?
To find the base, look for a multiple of a power of 10 that the numbers are close to. For example, if the numbers are close to 60, then the base would be 10 * 6 = 60.
Q: What is the purpose of finding the deviation in this multiplication method?
The deviation helps determine the difference between each number and the base. It is calculated by subtracting the base from the given number.
Q: How do you find the sum and product in this multiplication method?
The sum is the result of adding the two diagonal numbers (deviations) on the left. The product is the multiplication of the two deviations on the right.
Q: Why is it necessary to multiply the number on the left by the multiplying factor?
Multiplying the number on the left by the multiplying factor is an additional step specific to this method. It accounts for the deviation caused by the base being a multiple of a power of 10.
Summary & Key Takeaways

When multiplying numbers that are not close to a power of 10, find the base by identifying a multiple of a power of 10 that the numbers are close to.

Calculate the deviation of each number from the base.

Find the sum of the deviations on the left and the product of the deviations on the right.

Multiply the number on the left by the multiplying factor and then add the righthand result to get the final answer.