Question

evaluate the following number 1 shortcut method (39)²

Answer 1

Method which can be used are given below,


1 : ( 39 )²



Splitting 39 in two numbers so that it will be in a form of a indentity [ ( a - b )² = a² + b² - 2ab ]


= > ( 40 - 1 )²

= > ( 40 )² + ( 1 )² - 2( 40 × 1 )

= > 1600 + 1 - 80

= > 1521



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2 : ( 39 )²



Splitting 39 in two numbers so that it will be in the form of a indentity [ ( a + b )² = a² + b² + 2ab ]


= > ( 30 + 9 )²

= > ( 30 )² + ( 9 )² + 2( 30 × 9 )

= > 900 + 81 + 540

= > 1521






3 : ( 39 )²



We know that any number with square in it is directly equal to the product of that number with itself.


= > 39 × 39

= > 1521






4 : ( 39 )²


We can simplify ( 3 ) ,


= > ( 39 ) × ( 39 )

= > ( 39 ) × ( 40 - 1 )

= > ( 39 ) × [ ( 4 × 10 ) - 1 ]

= > ( 4 × 39 × 10 ) - 39

= > ( 156 × 10 ) - 39

= > 1560 - 39

= > 1521