Example (1) 8*73+52*8 =8*（73+52） =8*125 =1000 Example (2) 9*96+3+9 =9*（96=3+1） =9*100 =900 For my daughter's homework, I don't know how to calculate, why to calculate like this, and why, exercises 1、 54 * 99 + 99 + 45 II. 54 + 99 * 99 + 45 3、 100 * 89 + 89 * 11 + 89 * 89 IV. 100 * 89-89 * 11-89 * 89 There is also the question 5*999+5+99*7+7+4*9+4=

Example (1) 8*73+52*8 =8*（73+52） =8*125 =1000 Example (2) 9*96+3+9 =9*（96=3+1） =9*100 =900 For my daughter's homework, I don't know how to calculate, why to calculate like this, and why, exercises 1、 54 * 99 + 99 + 45 II. 54 + 99 * 99 + 45 3、 100 * 89 + 89 * 11 + 89 * 89 IV. 100 * 89-89 * 11-89 * 89 There is also the question 5*999+5+99*7+7+4*9+4=

Question 1. Factorization, merging similar items, 8 * 73 and 8 * 52 have 8, so put forward 8, 73 + 52 is exactly equal to 125, 8 * 125 oral calculation can get the answer, generally there will be such a question of 8 * 73 + 4 * 104, need to change the back into 8 * 52, in short, through the formula deformation and simplification, try to achieve the degree of oral calculation