1. 计算 $1 - (-1)$ 的结果是( )
A.$2$
B.$1$
C.$0$
D.$-2$
A.$2$
B.$1$
C.$0$
D.$-2$
答案:
A
2. 下列计算中,正确的是( )
A.$-3 - 7 = -3 + 7 = 4$
B.$4.5 - 6.8 = 6.8 - 4.5 = 2.3$
C.$-2 - (-\frac{1}{3}) = -2 + \frac{1}{3} = -2\frac{1}{3}$
D.$-3 - (-\frac{1}{2}) = -3 + \frac{1}{2} = -2\frac{1}{2}$
A.$-3 - 7 = -3 + 7 = 4$
B.$4.5 - 6.8 = 6.8 - 4.5 = 2.3$
C.$-2 - (-\frac{1}{3}) = -2 + \frac{1}{3} = -2\frac{1}{3}$
D.$-3 - (-\frac{1}{2}) = -3 + \frac{1}{2} = -2\frac{1}{2}$
答案:
D
3. 某地元旦的最高气温是 $9^{\circ}C$,最低气温是 $-2^{\circ}C$,则该地这天的最低气温比最高气温低( )
A.$7^{\circ}C$
B.$-7^{\circ}C$
C.$11^{\circ}C$
D.$-11^{\circ}C$
A.$7^{\circ}C$
B.$-7^{\circ}C$
C.$11^{\circ}C$
D.$-11^{\circ}C$
答案:
C
4. 填空:
(1) $3 - (-1) =$ ______.
(2) $(-10) - 3 =$ ______.
(3) $33 - (-27) =$ ______.
(4) $0 - 12 =$ ______.
(1) $3 - (-1) =$ ______.
(2) $(-10) - 3 =$ ______.
(3) $33 - (-27) =$ ______.
(4) $0 - 12 =$ ______.
答案:
(1)4
(2)-13
(3)60
(4)-12
(1)4
(2)-13
(3)60
(4)-12
5. 填空:
(1) 比 $2^{\circ}C$ 低 $8^{\circ}C$ 的温度是 ______ $^{\circ}C$.
(2) 比 $-3^{\circ}C$ 低 $6^{\circ}C$ 的温度是 ______ $^{\circ}C$.
(3) 比 $0$ 小 $4$ 的数是 ______.
(4) 比 $0$ 小 $-4$ 的数是 ______.
(5) $7.4$ 比 $8.3$ 小 ______.
(6) $7.4$ 比 $8.3$ 大 ______.
(1) 比 $2^{\circ}C$ 低 $8^{\circ}C$ 的温度是 ______ $^{\circ}C$.
(2) 比 $-3^{\circ}C$ 低 $6^{\circ}C$ 的温度是 ______ $^{\circ}C$.
(3) 比 $0$ 小 $4$ 的数是 ______.
(4) 比 $0$ 小 $-4$ 的数是 ______.
(5) $7.4$ 比 $8.3$ 小 ______.
(6) $7.4$ 比 $8.3$ 大 ______.
答案:
(1)-6
(2)-9
(3)-4
(4)4
(5)0.9
(6)-0.9
(1)-6
(2)-9
(3)-4
(4)4
(5)0.9
(6)-0.9
6. 在 $-\frac{1}{2},0,25\%,|-3|,1.2,8,-2,\frac{3}{2}$ 中,自然数有 $a$ 个,分数有 $b$ 个,负数有 $c$ 个,则 $a - b - c =$ ______.
答案:
-3[解析]由题意,得a=3,b=4,c=2,则a - b - c=-3.
7. 计算:
(1) $0 - (-12)$.
(2) $\frac{5}{2} - (-2.5)$.
(3) $(-\frac{3}{4}) - (+\frac{1}{2})$.
(4) $2\frac{1}{8} - 3\frac{1}{2}$.
(5) $7.2 - (-2.8) - (+5)$.
(1) $0 - (-12)$.
(2) $\frac{5}{2} - (-2.5)$.
(3) $(-\frac{3}{4}) - (+\frac{1}{2})$.
(4) $2\frac{1}{8} - 3\frac{1}{2}$.
(5) $7.2 - (-2.8) - (+5)$.
答案:
解:
(1)原式=0+12=12.
(2)原式=$\frac{5}{2}$+2.5=5.
(3)原式=$-\frac{3}{4}$+(-$\frac{1}{2}$)=$-\frac{3}{4}$+(-$\frac{2}{4}$)=-1$\frac{1}{4}$.
(4)原式=2$\frac{1}{8}$-3$\frac{4}{8}$=-1$\frac{3}{8}$.
(5)原式=7.2+2.8+(-5)=10 +(-5)=5.
(1)原式=0+12=12.
(2)原式=$\frac{5}{2}$+2.5=5.
(3)原式=$-\frac{3}{4}$+(-$\frac{1}{2}$)=$-\frac{3}{4}$+(-$\frac{2}{4}$)=-1$\frac{1}{4}$.
(4)原式=2$\frac{1}{8}$-3$\frac{4}{8}$=-1$\frac{3}{8}$.
(5)原式=7.2+2.8+(-5)=10 +(-5)=5.
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