A simple way to do 7 times 8 times 9 times 10 times 11 times 12 times 13?

Multiply an even number by 5, multiply an odd number by 10, and finally multiply by one. I don't know if it's right. (*Hee-hee.......)Don't blame me for being wrong.

Multiplication rules such as 11 times 11 or 12 times 12 and 13 times 13 can be factored by a perfect square number.

Perfect square number factorization formula: n = 1 + 1 + 2 + 2 + n 1 + n 1 + n.

According to the formula: 11x11=11=10 +10+11=100+21=121

12x12=12²=10²+10+11+11+12=100+44=144

13x13=13²=10²+10+11+11+12+12+13=100+69=169

Using this formula, you can find the square number by remembering the square number of a number that is close to the square number you are looking for, for example: 52 = 50 +50+51+51+52=2500+204= 2704.

8 13 7 15) 13 15

Modal first (8 15-7 8) closed roll (13 15) (13 15) 8 15-7 8

8 (15-7).

Untie; Swift repentance = (8 Qi Changzi 13-7 15)·13·15=8 13·13·15-7 Gao Jue 15·13·15=8·1·15-7·13·1=120-91=29.

Solution: Original form.

125x8)x(17x3)

1000x51

Method: The associative law of multiplication was used to achieve simple calculation.

Untie; Swift repentance = (8 Qi Changzi 13-7 15)·13·15=8 13·13·15-7 Gao Jue 15·13·15=8·1·15-7·13·1=120-91=29.

Since there are 12 in both multiplications, the inverse of the multiplication assignment is 12 (77+13)=1080

Crack and burn, happy to answer for you.

Dear, if it helps, please Duan Nai and Dianyi to get a like, thank you.