1.ç²ãä¹ä¸¤è½¦åå«ä»AãB两å°åæ¶åºåï¼ç¸åèè¡ï¼å¨AãB两å°ä¹é´ä¸åå°å¾è¿è¡é©¶ï¼å·²ç¥ä¸¤è½¦å两次ç¸éå°ç¹çè·ç¦»æ¯AãB两å°è·ç¦»ç1/4ï¼å¦æç²è½¦è¡é©¶é度æ¯ä¹è½¦å¿«ï¼é£ä¹ç²ãä¹ä¸¤è½¦çé度ä¹æ¯ä¸º9:7ã
解ï¼è®¾AãB两å°è·ç¦»ä¸ºsï¼ç²è½¦è¡é©¶é度为uï¼ä¹è½¦é度为vï¼å第ä¸æ¬¡ç¸éç²è½¦è¡é©¶è·ç¦»ä¸ºu*s/(u+v)ï¼ä¹è½¦è¡é©¶è·ç¦»ä¸ºv*s/(u+v)
è¿éæ两ç§æ
åµï¼ä¸æ¯ä¹è½¦æªå°Aå°å°±è¢«ç²è½¦è¿½ä¸ï¼äºæ¯ä¹è½¦å°äºAå°å头ä¸ç²è½¦ç¸é
1ï¼ç¬¬äºæ¬¡ç¸éç²è½¦è¡é©¶è·ç¦»ä¸º(v*s/(u+v))*2+s/4ï¼ä¹è½¦è¡é©¶è·ç¦»ä¸ºs/4
((v*s/(u+v))*2+s/4)/u=(s/4)/v
2v^2/(u+v)+v/4=u/4
8v^2+v(u+v)=u(u+v)
9v^2-u^2=0
(3v-u)(3v+u)=0
3v=uï¼u:v=3:1
2ï¼ç¬¬äºæ¬¡ç¸éç²è½¦è¡é©¶è·ç¦»ä¸º(v*s/(u+v))*2+s/4ï¼ä¹è½¦è¡é©¶è·ç¦»ä¸ºu*s/(u+v)+s(1-1/4)-v*s/(u+v)
((v*s/(u+v))*2+s/4)/u=(u*s/(u+v)+s(1-1/4)-v*s/(u+v))/v
2v^2/(u+v)+v/4=u^2/(u+v)+3u/4-uv/(u+v)
8v^2+v(u+v)=4u^2+3u(u+v)-4uv
9v^2+2uv-7u^2=0
(9v-7u)(v+u)=0
9v=7uï¼u:v=9:7
æ ¹æ®é¢æï¼ç¬¬äºæ
åµè¾åéã
2.ç²ãä¹ä¸¤äººä»ä¸æ¡ç¯å½¢è·éä¸åä¸å°ç¹åæ¶åºåï¼æ²¿ç¸åæ¹åè·ï¼æ¯äººè·å®ç¬¬ä¸åå°è¾¾åºåç¹åç«å³å头åéè·ç¬¬äºåï¼é¡ºæ¶éæ¶ï¼ç²æ¯ç§è·4ç±³ï¼ä¹æ¯ç§è·5ç±³ï¼éæ¶éæ¶ï¼ç²æ¯ç§è·5ç±³ï¼ä¹æ¯ç§è·6ç±³ãé£ä¹ç²ãä¹ä¸¤äººå次è·ååºåç¹æ¯ç¬¬54次ç¸éã
解ï¼è®¾ç¯å½¢è·éé¿ä¸ºs
è¿éæ两ç§æ
åµï¼ä¸æ¯ç²ç¬¬ä¸åå
顺æ¶éè·ï¼äºæ¯ç²ç¬¬ä¸åå
éæ¶éè·ï¼å®é
ä¸ä¸¤ç§æ
åµæ¯ä¸æ ·çã
ç²ç¬¬ä¸åç¨æ¶s/4ï¼ç¬¬äºåç¨æ¶s/5ï¼ä¸¤åç¨æ¶s/4+s/5=9s/20
ä¹ç¬¬ä¸åç¨æ¶s/5ï¼ç¬¬äºåç¨æ¶s/6ï¼ä¸¤åç¨æ¶s/6+s/5=11s/30
设ç²è·äºn个两å两人å次è·ååºåç¹
è¦ä½¿9ns/20/(11s/30)= 27n/22为æå°æ´æ°ï¼n=22
ä¹è·äº27个两åï¼æ¯åé½ä¼ä¸ç²ç¸éä¸æ¬¡ï¼å
±ç¸é27*2=54次ã
3ã2008/2008+(2007/2008-2007/2007)+(2006/2008-2006/2007+2006/2006)+ â¦+(1/2008-1/2007+1/2006-1/2005+â¦+1/2-1/1)
解ï¼åå¼=(2008+2007+2006+â¦+1)/2008-(2007+2006+â¦+1)/2007+(2006+2005+â¦+1)/2006-(2005+2004+â¦+1)/2005+â¦+(2+1)/2-1/1
=2009Ã2008/2/2008-2008Ã2007/2/2007+2007Ã2006/2/2006-2006Ã2005/2/2005+â¦+3Ã2/2/2-2Ã1/2/1
=2009/2-2008/2+2007/2-2006/2+â¦+3/2-2/2
=1/2Ã2008/2
=502
4ãå°èç¬å±±ï¼ä¸å±±çå¹³åé度æ¯æ¯å°æ¶2åç±³ï¼å°è¾¾å±±é¡¶åç«å³ä¸å±±ï¼ä¸å±±çå¹³åé度æ¯æ¯å°æ¶6åç±³ãå°èä¸ãä¸å±±çå¹³åé度æ¯æ¯å°æ¶ï¼3)åç±³ã
解ï¼è®¾å±±ä¸å°å±±é¡¶è·¯ç¨ä¸ºxãåå¹³åé度为ï¼
2x÷ï¼x÷2+x÷6ï¼=12x÷ï¼3x+xï¼=3
5ã快车æ¯ç§è¡24ç±³ï¼æ
¢è½¦æ¯ç§è¡21ç±³ãç°å¨ä¸¤è½¦è½¦å¤´å¹¶é½ï¼ç»è¿30ç§å¿«è½¦ç车尾离å¼æ
¢è½¦ç车头ï¼ç°å¨ä¸¤è½¦è½¦å°¾å¹¶é½ï¼ç»è¿45ç§å¿«è½¦ç车尾离å¼æ
¢è½¦ç车头ãå¦æ两åç«è½¦ç¸åèè¡ï¼ä»è½¦å¤´ç¸éå°è½¦å°¾ç¦»å¼å
±ç¨ï¼5ï¼ç§ã
解ï¼å¿«è½¦é¿åº¦ï¼30*ï¼24-21ï¼=90 m
æ
¢è½¦é¿åº¦ï¼45*ï¼24-21ï¼=135 m
ç¸éæ¶é´T=ï¼135+90ï¼/ï¼24+21ï¼=5 s
6ã100个人åçäºéé¢ãæ82人ç对第ä¸é¢ï¼æ90人ç对第äºé¢ï¼æ89人ç对第ä¸é¢ï¼æ75人ç对第åé¢ï¼æ74人ç对第äºé¢ãç对ä¸é¢æä¸é¢ä»¥ä¸ç人ç®åæ ¼ãé£ä¹ï¼å¨è¿100人ä¸ï¼è³å°æï¼70ï¼äººåæ ¼ã
解ï¼æ±æå¤å 人ä¸åæ ¼å°±å¯ä»¥äºã
å
±çé 18+10+11+25+26 = 90é¢
ä¸åæ ¼äººæ¯äººåªé3é¢ 90/3 =30
é£ä¹åæ ¼ç人è³å°æ100-30=70人
åæ ¼ç人é½æ¯æ»¡åã
7ãå
¬å¸ä»æå°è¿æ¥ä¸æ¹é¶ç·è±ç¶ï¼æåäº50个ãè¥æå©ä¸çæ10å
ä¸ä¸ªåºå®ï¼åè¦äº300å
ï¼è¥å ä»·2å
åºå®ï¼åå¯çå©800å
ãå
¬å¸å
±è¿æ¥ï¼600ï¼ä¸ªé¶ç·è±ç¶ã
解ï¼è®¾å
¬å¸å
±è¿æ¥x个é¶ç·è±ç¶ï¼æ¯ä¸ªä»·æ ¼yå
ï¼åå¯å¾æ¹ç¨ï¼
10(x-50)=xy-300
(10+2)(x-50)=xy+800
2(x-50)=1100
x=600
8ãäºä¸ªæ°ä¸ï¼ä»»åå个æ°çå¹³åæ°åå ä¸ä½ä¸çä¸ä¸ªæ°ï¼æå¾çååå«æ¯74ã80ã98ã116ã128ï¼é£ä¹äºä¸ªæ°ä¸çæå°æ°æ¯æ大æ°å°ï¼72ï¼ã
设äºä¸ªæ°åå«æ¯aãbãcãdãeï¼å(a+b+c+d)/4+e=74
(b+c+d+e)/4+a=80
(c+d+e+a)/4+b=98
(d+e+a+b)/4+c=116
(e+a+b+c)/4+d=128
æå°æ¯eï¼æ大æ¯dã
(a+b+c+d+e)*2=74+80+98+116+128=496
a+b+c+d+e=496/2=248
(a+b+c+d+e)/4+3e/4=74
e=4(74-248/4)/3=16
(e+a+b+c+d)/4+3d/4=128
d=4(128-248/4)/3=88
88-16=72
9ãä¸èè¹ï¼ç¬¬ä¸æ¬¡é¡ºæ°´èªè¡420åç±³ï¼éæ°´èªè¡80åç±³ï¼ç¨11å°æ¶ï¼ç¬¬äºæ¬¡ç¨åæ ·çæ¶é´é¡ºæ°´èªè¡240åç±³ï¼éæ°´èªè¡140åç±³ãè¿èè¹é¡ºæ°´è¡198åç±³éè¦ï¼3.3ï¼å°æ¶ã
解ï¼è®¾å°è¹å¨éæ°´ä¸çéåº¦æ¯ x åç±³/å°æ¶ï¼æ°´éæ¯ y åç±³/å°æ¶ã
å¯åæ¹ç¨ç»ï¼420/(x+y)+80/(x-y)=11 ï¼240/(x+y)+140/(x-y)=11ï¼
å¾x=40ï¼y=20ï¼
198/(40+20)=3.3ã
10ãç²ä¹ä¸¤è½¦åæ¶ä»AãB两å°åºåç¸åèè¡ï¼å¨è·Bå°108åç±³å¤ç¸éãå®ä»¬åèªå°è¾¾å¯¹æ¹åºåå°åç«å³è¿ååå°ï¼éä¸åå¨è·Aå°84åç±³å¤ç¸éã两次ç¸éå°ç¹ç¸è·ï¼48ï¼åç±³ã
解ï¼è®¾ç²éV1,ä¹éV2ï¼ç¬¬ä¸æ¬¡ç¸éèæ¶tï¼AãB两å°è·ç¦»S,
å V2*t=108; V1*t+108=S å¾åºï¼V1*108/V2+108=S ä¹å³ï¼V1/V2=(S-108)/108
第äºæ¬¡ç¸éæ¶é´ç¸çï¼å¾åºï¼(S-108+84)/V2=(108+S-84)/V1 ä¹å³ï¼V1/V2=(S+24)/(S-24)
(S-108 )/108=(S+24)/(S-24)å¾åºï¼S=240
æ以ï¼ç¸éå°ç¹è·ç¦»=240-108-84=48åç±³
11ãå¼åï¼â³ÃâÃâ³â=âââï¼â³â代表ä¸ä¸ªä¸¤ä½æ°ï¼âââ代表ä¸ä½æ°ï¼æ±â³=ï¼â=ï¼å¹¶åè¿ç¨
解ï¼â³åâé½ä¸è½ä¸º0
âââæ¯ä¸ä¸ªä¸ä½æ°åç¸åçä¸ä½æ°ï¼è¢«111æ´é¤
111=3Ã37
â´â³â=37ï¼â=7ï¼â³=3
çï¼â³=3ï¼â=7ã
12ãAï¼Bä¸äºè´¨,AãBçæ大å
¬çº¦ä¸æå°å
¬åæ°å为35,A+Bçæå°æ¯å¤å°
解ï¼è®¾d=(Aï¼B)ï¼åA=A/dÃdï¼B=B/dÃdï¼[Aï¼B]=AB/d=A/dÃB/dÃdï¼
[Aï¼B]+d=35=5Ã7=(A/dÃB/d+1)Ãd
d=5æ7
å½d=5æ¶ï¼A/dÃB/d+1=7ï¼A/dÃB/d=6=2Ã3=1Ã6
A=5ï¼B=30æA=10ï¼B=15
å½d=7æ¶ï¼A/dÃB/d+1=5ï¼A/dÃB/d=4=2Ã2=1Ã4
A=14ï¼B=14ä¸åé¢æï¼A=7ï¼B=28
A=10ï¼B=15æ¶ï¼A+B=25æå°
çï¼A+Bçæå°æ¯25ã
13ï¼å¨æ°å1/1ï¼2/1ï¼1/2ï¼3/1ï¼2/2ï¼1/3ï¼4/1ï¼3/2ï¼2/3ï¼1/4â¦â¦ä¸ç¬¬2006个æ°ä¸ºå¤å°ï¼
解ï¼63*64/2=2016>2006
1+2+3+â¦â¦+62=1953
2006-1953=53
(63+1-53)/53=11/53
çï¼ç¬¬2006个æ°ä¸º11/53ã
14ï¼ç²ä¹ä¸¤æ¡¶æ²¹å
±é360åå
ï¼ä»ç²æ¡¶ååº4åä¹1ï¼ä»ä¹æ¡¶ååº3åä¹1ï¼è¿æ¶ç²æ¡¶å©ä¸çæ²¹æ¯ä¹æ¡¶å¤7åä¹2ï¼åæ¥ç²æ¡¶ææ²¹å¤å°åå
ï¼
解ï¼ç²*(1-1/4)-(360-ç²)*(1-1/3)=(360-ç²)*(1-1/3)*2/7
ç²*3/4=(360-ç²)*2/3*9/7
21ç²=24(360-ç²)
45ç²=24*360
ç²=192
ä¹=360-192=168
çï¼åæ¥ç²æ¡¶ææ²¹192åå
15ï¼å°æ³åå°ç¾åå«ä»Aï¼B两å°åæ¶åºåç¸åèè¡ãåºåæ¶ä»ä»¬çé度ä¹æ¯æ¯3ï¼2ï¼ä¸¤äººç¸éåï¼å°æ³çé度æé«äºç¾åä¹20ï¼å°ç¾çé度æé«äºç¾åä¹50ãå½å°æ³å°è¾¾Bå°æ¶ï¼å°ç¾ç¦»Aå°è¿æ4åç±³ãAï¼B两å°çè·ç¦»æ¯å¤å°åç±³ï¼
解1ï¼è®¾Aï¼B两å°çè·ç¦»æ¯xåç±³ï¼å°ç¾æéåçé度为vï¼åå°æ³æéåçé度为vÃ3/2=1.5v
x÷(v+1.5v)Ã1.5v=x÷(v+1.5v)Ãv÷(1.5v+20%Ã1.5v)Ã(v+50%v)+4
x÷2.5Ã1.5=x÷2.5÷(1.8v)Ã(1.5v)+4
3x/5=2x/5Ã5/6+4
18x=10x+120
8x=120
x=15
çï¼Aï¼B两å°çè·ç¦»æ¯15åç±³ã
解2ï¼å°æ³åå°ç¾ç¸éæç¨çæ¶é´ç¸çï¼ä»ä»¬çé度æ¯çäºæè¡çè·¯ç¨æ¯
ç¸éæ¶ï¼å°æ³è¡äºå
¨ç¨ç3/(3+2)=3/5ï¼å°ç¾è¡äºå
¨ç¨ç2/(3+2)=2/5
æéåï¼å°ç¾éï¼å°æ³é=2(1+50â
)ï¼3(1+20â
)=5ï¼6ï¼åæ ·å¨ç¸åæ¶é´å
ï¼é度æ¯çäºè·¯ç¨æ¯ï¼å°ç¾è¡è·¯ç¨æ¯å°æ³è¡è·¯ç¨ç5/6
å½å°æ³å°è¾¾Bå°æ¶ï¼å°ç¾åå°æ³åè¡äºå
¨ç¨ç2/5ï¼å°ç¾åºè¯¥è¡äºå
¨ç¨ç2/5Ã5/6=1/3
4å米就ç¸å½äºå
¨ç¨ç(3/5-1/3)
AãB两å°çè·ç¦»=4÷(3/5-1/3)
=4÷4/15
=15åç±³
综åç®å¼ï¼
4÷{3/(3+2)-[2/(3+2)]Ã[2(1+50â
)]÷[3(1+20â
]}
=4÷[3/5-2/5Ã3÷3.6]
=4÷(3/5-1/3)
=4÷4/15
=15åç±³
çï¼AãB两å°çè·ç¦»æ¯15åç±³ã
16ãæä¸æ®µè·¯é¿230åç±³ï¼æ车å»æ¶ç¨4.5å°æ¶ï¼è¿åæ¶ç¨4.45å°æ¶ï¼å·²ç¥å¹³è·¯60åç±³/å°æ¶ï¼ä¸å¡è·¯40åç±³/å°æ¶ï¼ä¸å¡è·¯50åç±³/å°æ¶ãæ±å¹³è·¯ãä¸å¡è·¯ãä¸å¡è·¯åå¤é¿ã
解ï¼è®¾å»æ¶å¹³è·¯é¿aåç±³ãä¸å¡è·¯é¿båç±³ï¼åä¸å¡è·¯é¿230-a-båç±³
a/60+b/40+(230-a-b)/50=4.5
a/60+b/50+(230-a-b)/40=4.45
3b+60=2a
5a+3b=780
a=120
b=60
230-a-b=50
çï¼å»æ¶å¹³è·¯é¿120åç±³ãä¸å¡è·¯é¿60åç±³ï¼åä¸å¡è·¯é¿50åç±³
温馨提示:答案为网友推荐,仅供参考