multiplying two ways 26x36

Question

what two ways can be used to solve this problem

Answer 1

Given: 26x36

1. 26X36=26x(6+30)=156+780=936

2. 26x36=(20+6)(30+6)=20x30+20x6+6x30+6x6=600+120+180+36=936

3. 26x36=(30-4)(30+6)=30x30+30x6-4x30-4x6=900+180-120-24=936*

4. 26x36=(30-4)(30+6)=30(30-4+6)-4x6=30x32-4x6=960-24=936*

* (a-b)(a+c)=a²+ac-ba-bc (for 3.) =a(a+c-b)-bc (for 4.)   Or, (a+b)(a+c)=a(a+b+c)+bc

For example, 24x18=(20+4)(20-2)=20(20+4-2)-4x2=20x22-4x2=440-8=432   22X23=20(20+2+3)+2x3=20x25+2x3=500+6=506, 111x97=(100+11)(100-3)=100x108-11x3=10800-33=10767