1. 直接写出得数。(20☆)
$6a + 8a = $
$6a + 4a - 2.5a = $
$y - 0.6y - 0.2y = $
$4 + b + b = $
$y + 3y = $
$7x + 13x = $
$5a×4 - a = $
$8a - 4a = $
$6x - 2x = $
$13c - 5c = $
$25x÷5 = $
$4×(25 + a) = $
$12m - 7m = $
$5n - 4n = $
$a + a = $
$8×(1.25 - b) = $
$3x + 6x = $
$(a + 5)×3 = $
$12a + 6a - 8a = $
$(2b + b)×3 = $
$11a - 7a = $
$25y + 75y = $
$n×1 = $
$2×a×b = $
$b - 0.3b = $
$x + 9x - 5x = $
$y×6×y = $
$5×(y + y) = $
$1.4y + 0.6y = $
$3(y - 2) = $
$k + k + k = $
$15×x÷3 = $
$68a + 32a = $
$125m - 25m = $
$a - 6.2 - 3.8 = $
$(2x - x)×3 = $
$15y÷3 = $
$15y - 10y = $
$(a×b)×c = $
$(2y + y)×10 = $

14a 7.5a 0.2y 4+2b 4y 20x 19a 4a 4x 8c 5x 100+4a 5m n 2a 10-8b 9x 3a+15 10a 9b 4a 100y n 2ab 0.7b 5x 6y² 10y 2y 3y-6 3k 5x 100a 100m a-10 3x 5y 5y abc 30y

2. 根据运算律在$□$里填上适当的数或字母。(10☆)
(1)$am - bm = ×( - )$
(2)$5.6x + 4.4x = ( + )×$
(3)$c×8×a = 8×$
(4)$2a + 3a = ( + )×a$

(1)m a b (2)5.6 4.4 x (3)a c (4)2 3

3. 分别用字母表示如图涂色部分的周长、面积,再计算当$a = 10cm$,$b = 7.2cm$,$c = 5.2cm$时涂色部分的周长、面积分别是多少? (8☆)
周长：，面积：
周长：
面积：

周长：2(a - b + c)，面积：ac - bc
周长：2×(10 - 7.2 + 5.2) = 16(cm)
面积：10×5.2 - 7.2×5.2 = 14.56(cm²)

4. 列竖式计算。(12☆)
$685÷0.25 = $
$0.384÷0.24 = $
$15.36÷0.12 = $

2740 1.6 128