1. | 2. | 3. | 4. |
A | C | B | C |
5. | 6. | 7. | / |
C | 3.5 | 2 | / |
(2)原式=24÷3×2=16.
(3)原式=(5/6-1/2+1/3)×6=(2/3)×6=4.
9.解:(1)因为∣a∣=5,∣b∣=3,
所以a=±5,6=±3.
因为a>0,b>0,所以a=5,b=3.
所以a+b=5+3=8,ab=5×3=15.
(2)因为∣a-2∣≥0,∣b-3∣≥0,∣c - 4∣≥0,∣a-2∣+∣ b-3∣+∣c-4∣=0,
所以a=2,b=3,c=4.
所以a+2b+3c =2+2×3+3×4=20.
10.解:(1)根据题意画草图(图略),由数轴易知他们没有回到出发点,而是在A地的南方,距离A地42 km.
(2)∣+22∣+∣-3∣+∣-4∣+∣-2∣+∣-8∣+∣+17∣+∣-2∣+∣+12∣+∣+7∣+∣-5∣
=22+3+4+2+8+17+2+12+7+5
=82(km),
82×0.08=6.56(L),
故这天共耗油6.56 L.