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How to Quickly Square any 2-digit Number Mentally


The above video by Mathemagician Art Benjamin shows an ingenious way of squaring any 2-digit numbers easily without a calculator. If you practice and master this technique, it serves as an amusing and fanciful trick to "show off" to you friends! Besides, it is also a good way to train your mental arithmetic skills.

Some examples that depicts his technique:

Pre-requisite to the trick:

You have to be proficient in multiplying a 2 digit by 1 digit number mentally.

Mathematics Behind it:

The math behind the technique is based on the "difference of 2 squares" identity that we learn in our secondary 2 math syllabus in Singapore.

Practice!

Practice LOTS to become really good at it!

Try squaring the following numbers and check with a calculator!

a) 41

b) 29

c) 37

d) 42

e) 38

f) 53

g) 69

h) 76

i) 67

j) 88

k) 94

l) 55

m) 73

n) 75

o) 19

Keep practicing and master this technique of squaring any 2-digit number quickly using mental arithmetic!

To get professional help (Math tuition) on secondary school mathematics in Singapore, click here.

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