Question

数学题：①.（4又7/8）-（-5又1/2）+（-4又1/4）-(3又1/8） ②（-4又7/9）-(3又1/6）-（2又2/9)+(-6又1/6

③.（-12.5）×（-6/7）×（-4） ④（-1/2+2/3+1/4-7/12+1)×（-12） ⑤ 3.14×（1/3）-3/4×3.14+1/2×3.14

Answer 1

①.（4又7/8）-（-5又1/2）+（-4又1/4）-(3又1/8）
= (4又7/8）+（5又1/2）-（4又1/4）-(3又1/8）
= (4+5-4-3) +(7/8+1/2-1/4-1/8）
= 2 + (7+4-2-1)/8
= 2 + 1
= 3
②（-4又7/9）-(3又1/6）-（2又2/9)+(-6又1/6
= -（4又7/9）-(3又1/6）-（2又2/9)-(6又1/6)
= -(4+3+2+6) - (7/9+1/6+2/9+1/6)
= -15 - (7/9+2/9+1/6+1/6)
= -15 - (1+1/3)
= -(16+1/3)
= ﹣16又1/3

③.（-12.5）×（-6/7）×（-4）
= - 12.5 × 6/7 ×4
= - 12.5 ×4 × 6/7
= - 50 × 6/7
= - 300/7
= -42又6/7

④（-1/2+2/3+1/4-7/12+1)×（-12）
= （1/2-2/3-1/4+7/12-1)×12
= 1/2×12 -2/3×12 -1/4×12 +7/12×12 -1 ×12
= 6 -8-3+7-12
= -10

⑤ 3.14×（1/3）-3/4×3.14+1/2×3.14
= 3.14×（1/3 - 3/4+1/2)
= 3.14×（4 - 9 + 6)/12
= 3.14×1/12
≈ 0.2617

Answer 2

1. = 39/8 + 22/4 - 17/4 - 25/8
= 14/8 + 5/4
= 7/4 + 5/4
= 3
2. = -43/9 - 19/6 - 20/9 - 37/6
= -63/9 - 56/6
= -7 - 28/3
= -16又1/3
3. = -50 * 6/7
= -300/7
= -42又6/7
4. = 6 - 8 - 3 + 7 -12
= -10
5. = 3.14 * (1/3 - 3/4 + 1/2)
= 3.14 * (4/12 - 9/12 - 6/12)
= 3.14 * 1/12
= 157/600

Answer 3

3.14×（1/3）-3/4×3.14+1/2×3.14
= 3.14×（1/3 - 3/4+1/2)
= 3.14×（4 - 9 + 6)/12
= 3.14×1/12
≈ 0.2617

Answer 4

1.（-4又7/8）-（-5又1/2）+（-4又1/4）-（+3又1/8）
=-4+5-4-3-7/8+1/2-1/4-1/8
=-6+1/2-1/4-(7/8+1/8)
=-7+1/4
=-(6又3/4)

Answer 5

3.14×（1/3）-3/4×3.14+1/2×3.14
= 3.14×（1/3 - 3/4+1/2)
= 3.14×（4 - 9 + 6)/12
= 3.14×1/12
≈ 0.2617