19 + 199 + 1999 +. + 199... 9 (20 9S)

19 + 199 + 1999 +. + 199... 9 (20 9S)

19 + 199 + 1999 +. + 199... 9 (20 9S)
=(20-1)+(200-1)+(2000-1)+…… +（200… 0 (20 zeros) - 1)
=20+200+2000+…… +200… 0 (20 zeros) - 1x20
=22…… 22 (20 2) 0-20
=22…… 22 (19 2) 00

19 + 199 + 1999 +... 199... 9 (10 9S)

22222222210

Simple operation 1.13 × 67 + 28 × 33-15 × 23 2.64.7 × 0.25 + 135.3 △ 4
I (@. @) (?.)
Please write the analysis, let me learn

1、13×67+28×33-15×23
=13x67+13x33+15x33-15x23
=13x(67+33)+15(33-23)
=13x100+15x10
=1300+150
=1450
2.64.7×0.25+135.3÷4
=64.7x1/4+135.3x1/47
=(64.7+135.3)x1/4
=200x1/4
=50

Simple algorithm of 28.67 + 3.2 * 286.7 + 573.4 * 0.05

28.67 + 3.2 * 286.7 + 573.4 * 0.05 split 286.7 into 28.67 * 10; split 573.4 into 28.67 * 20, then the original formula becomes = 28.67 + 3.2 * (28.67 * 10) + (28.67 * 20) * 0.05, then remove the brackets, calculate 3.2 * 10 and 20 * 0.05, and it becomes 28.67 + 32 * 28.67 + 28.67 * 1

28.67x67 + 3.2 × 286.7 + 573.4 × 0.05 3 ^ (3x
28.67x67 + 3.2 × 286.7 + 573.4 × 0.05 3 ^ (3x4) ^ (4 × 5) ^ (5x6) ^ (6 ^ 7) ^ (7x8) ^ (8x9) (simple calculation)

28.67x67 x 3.2 × 286.7 + 573.4 × 0.05 = 286.7x6.7 x 3.2 × 286.7 + 286.7 × 0.1 = 286.7 × (6.7 + 3.2 + 0.1) = 286.7 × 10 = 28673 ^ (3 ^ 4) ^ (4 ^ 5) ^ (5 ^ 6) ^ (6 ^ 7) ^ (7 ^ (8 ^ (8 ^ 9) in the middle of brackets is ^ = 3 ^ 3 × 4 ^ 4 × 5 ^ 5 × 6 ^ 6

28.67×67+3.2×286.7+573.4×0.05=

28.67×67+3.2×286.7+573.4×0.05=28.67 * 67 + 28.67 * 10 * 3.2 + 28.67 * 20 * 0.05 = 28.67 (67 + 32 + 1) =28.67 *100 = 2867
(train of thought: when I look at this question, I see that 28.67, 286.7 and 573.4 have 10 times and 20 times relationships respectively.)

There are four classes in grade one, 83 in class one and class two, 86 in class two and class three, 88 in class three and class four, and how many in class one and class four

There are X students in class one, y students in class two, Z students in class three and t students in class four
X+Y=83
Y + Z = 86 leads to Z = x + 3
Z+T=88
Substituting z = x + 3 into Z + T = 88, we can get x + T = 85, that is, the number of class one and class four

0.75 * 99 + 0.7 how easy and urgent! Homework!

0.75*99+0.7
=0.75*（100-1）+0.7
=75-0.75+0.7
=74.95

Simple operation of 99 * 0.75 + quarter × 99
Two and a quarter - one and two thirds + one and a sixth △ one and a ninth

99 * 0.75 + quarter × 99
=99*0.75+0.25×99
=99x（0.75x0.25）
=99x1
=99

7.536×99+75.36×0.1

7.536×99+75.36×0.1
=7.536×99=7.536×1
=7.536×（99+1）
=7.536×100
=753.6