# MSC #7 – Completing the Whole: Subtraction

Yesterday, we showed that “completing the whole” can greatly simplify addition. Today we will apply this technique in subtraction – specifically in computing the elapsed time.

Like computations using feet and inches, calculations involving time are more difficult for young learners because they are not based in the decimal system. This is especially true when the solution requires regrouping.

By adding 4 minutes to both the starting and ending times, we made the subtrahend (the starting time) “whole” as shown above. We can then determine the length of the movie without any difficulty.

As we have written yesterday, more variations of “completing the whole” in arithmetic operations will be demonstrated by Ms. Ginalyn Broquesa, coach of the Jose Rizal Memorial School in the opening plenary session of the “Inspirational Maths from India (Year 4)” on December 4, 2021.

“Completing the Whole“ is also discussed in Kenneth William’s online courses “Introduction to Vedic Mathematics“ and “Vedic Mathematics Teacher Training Course”.

It is also the subject of Chapter 6 of the “30 Master Strategies in Computing, Vol I” co-authored by Veronica and Virgilio Prudente.