Tag Archives: dividing by 2

Converting Fahrenheit to Celsius

To convert Fahrenheit to Celsius, we use the following formula,

C = 5/9 (F – 32) = 10/18 (F – 32)

The trick here is to recognize that 5/9 is the same as 10/18. Hence after deducting 32, we add a zero (multiply by 10) to the result and successively dividing by 2 and 9 (MSC 11 – Dividing by 9) to effectively divide by 18.

Step 1. Subtract 32
Step 2. Multiply by 10
Step 3. Divide by 2
Step 4. Divide by 9

Let us solve look at some examples.

Example 1: 100 ^oF = 37.8 ^oC

Step 1. Subtract 32: 100 – 32 = 68
Step 2. Multiply by 10: 68 x 10 = 680
Step 3. Divide by 2: 680 ÷ 2 = 340
Step 4. Divide by 9: 340 ÷ 9 = 37 r. 7 = 37.7… = 37.8

Example 2: 145^oF = 62.8^oC

Step 1. Subtract 32: 145 – 32 = 113
Step 2. Multiply by 10: 113 x 10 = 1130
Step 3. Divide by 2: 1130 ÷ 2 = 565
Step 4. Divide by 9: 565 ÷ 9 = 62 r. 7 = 62.7… = 62.8

Easy and simple!

MSC 6 – Dividing by 2

Dividing a number by 2 is also called halving.

Dividing a number by 2 can be simplified by splitting the number into smaller, more manageable parts. It can be done in a step by step fashion to make the procedure easier.

Half of 8 is 4.
Half of 40 is 20.
Half of 10 is 5.
Half of 30 is 15.
Half of 900 is 450.

Example 6.1 46÷2

= half of 40 + half of 6= 20 + 3

= 23

Example 6.2: 58 ÷2

= half of 50 + half of 8= 25 + 4

= 29

Example 6.3: 908 ÷2

= half of 900 + half of 8= 450 + 4

= 454

Longer numbers can be split.

Example 6.4 5046 ÷2

= 50|46 ÷2= 25|23

Some prefer to solve Ex. 6.2 as follows:

Example 6.5: 58 ÷2

= half of 40 + half of 18= 20 + 9

= 29

The preceeding example leads to another procedure of dividing by 2, which can be developed further into a single-line division technique.

Example 6.6: 3, 742 ÷2 =

Step 1) 3 divided by 2 is 1 remainder 1.

Step 2) The remainder becomes the first digit of the next dividend 17, which when divided by 2 will give 8 and a remainder of 1.

Step 3) The next dividend will then be 14 (first digit is the remainder of 1 from the previous operation) which evenly divides to give 7.

Step 4) The last digit of the dividend is 2 which gives 1 when halved.

The final answer is 1871.

Example 6.7: 5789 ÷2 =

5₁7 8 9 ÷ 2 = 2 5 divided by 2 is 2 remainder 1

5₁7₁8 9 ÷ 2 = 28 17 divided by 2 is 8 remainder 1

5₁7₁8 9 ÷ 2 = 289 18 divided by 2 is 9, no remainder

5₁7₁8 9.₁0 ÷ 2 = 2894 9 divided by 2 is 4 remainder 1

5₁7₁8 9.₁0 ÷ 2 = 2894.5 10 divided by 2 is 5 no remainder.

Exercise 6: Halve the following numbers

1) 468

2) 1,264

3) 3,456

4) 2,752

5) 2,526

6) 7,338

7) 5,372

8) 6,784

9) 8,357

10) 101,303

Answers to all exercises are found in the answer key.

Discover the 25 Math Short Cuts ( 25 MSC )!

25 Math Short Cuts

By Ike Prudente

This collection of 25 Math Short Cuts is published in commemoration of the 25th Foundation Day of MSC Institute of Technology.

I have selected what I think will be most useful for everyone, whether you are students, teachers, professionals or plain folks who need to calculate every day. Much of the hard work in compiling this work is not in researching for materials because I know these short cuts by heart but in selecting what short cuts to include.

From our grade school years, many of us have learned many ways of simplifying calculations. I am sure that for most of us, “multiplying by 10” is one of the first math short cut we have learned. And we continue to use it, which is the reason why I did not include it here. Unfortunately, most of us have forgotten most of the short cuts we have been taught in the past. As for my case, I am somewhat “lazy” at calculations so that I always looked for easier ways of computing. From my grade four teacher, I learned “squaring numbers ending in 5’ To this was added some more techniques which I picked-up from various books. I developed more short cuts by applying what I learned in algebra to simplify arithmetic computations. Then there were also some “tricks” I learned when I began to study “Vedic Math” in 2003, when they became available in the Internet.

$Math Short Cuts$

Even very young children can learn math short cuts, even adding left-to-right ( versus the traditional right to left )

I observed that my students enjoyed the short cuts that I shared with them and many came to love Math and actually improved their grades in the subject. I am also sure that these short cuts helped countless of my students pass the Philippine Science High School, UP Rural High School and UP entrance examinations.

Realizing that most readers like me, don’t want to read explanations, I will try to present the techniques in the form of examples, avoiding long explanations as much as possible. But sometimes we will cite Sutras or “word formulas” used in Vedic Math, which are very useful in remembering the short cuts.

We hope that with these shortcuts you will eventually be able to do most calculations mentally. However, we also realize that many will have to write down the answer first before reciting it. So we will explain the procedures to arrive at a written answer using a mental solution. With a little practice, many can dispense with the written answer.

Math Short Cuts (MSC)

We will add one short cut every week until Foundation Day 2014

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Tag Archives: dividing by 2

Converting Fahrenheit to Celsius

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Math Short Cuts (MSC)

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