0

15 x 61 = (15)·(61) = (10 + 5)·(60 + 1)
= 6x100 + 1x10 + (   )x10 + 5
= 600 + 10 + (   )x10 + 5 =     915

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FirstOuterInnerLast

 

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How Many

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FOIL method @

 

Example >>>

 34 x 52 =  (30 + 4)·(50 + 2)

 

 

 

 

First

(A + B)·(C + D) = AC + AD + BC + BD

= 30 x 50

= 1500

Outer

(A + B)·(C + D) = AC + AD + BC + BD

= 30 x 2

=     60

Inner

(A + B)·(C + D) = AC + AD + BC + BD

= 4 x 50

=   200

Last

(A + B)·(C + D) = AC + AD + BC + BD

= 4 x 2

=       8

 

 

   

 

 

 

= 1768