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Anonymous users2024-02-06Let's do two questions, just practice the pen.
1.The "Snow Dragon" scientific research ship went to Antarctica to carry out scientific research activities, and it took more than 30 days to sail from Shanghai at a maximum speed of 19 knots (1 knot = 1 nautical mile hour) to reach Antarctica. The ship departed from Shanghai at a speed of 16 knots and arrived at its destination a few days later.
After working in the polar regions for several days, returning at a speed of 12 knots, sailing at a speed of 2 knots on the 83rd day after departing from Shanghai due to weather conditions, and returning to Shanghai at a speed of 14 knots for 4 days after 2 days, how many days did the "Snow Dragon" work in Antarctica?
2。A, B, and C set off at the same time, where C rode from town B to town A, and A and B both went from town A to town B (A drove a car at a speed of 24 kilometers per hour, and B walked at a speed of 4 kilometers per hour), and when C and A met in town D on the way, they rode back to town B, and A turned around to pick up B. After A picks up B (B gets into A's car) and goes to Town B at a speed of 88 kilometers per hour, and the three of them arrive at Town B at the same time, then how many kilometers per hour does C ride the bike?
Answer: 1Solution: Let the distance of ab be s, the meeting time of A and C is t1, and the meeting time of A and B is t2. Later, the time when 3 people went to B at the same time was T3! C velocity is x
(24+x)t1=s
24+4）t2=（24-4）t1 ②
4（t1+t2）88+t3=s ③
x（t2+t3）=xt1 ④
Deduce, t2=5 7t1
From , t3 = 2 7t1
Put and substitute , get.
224/7t1=s ⑦
Put substitution in, got.
x=82.Answer and process: Solution: Set x days when going and work y days, where x is greater than 30. The equation is obtained:
16x=12（82-x-y）+2*2+14*4
16x=984-12x-12y+60
28x+12y=1044
7x+3y=261
As mentioned above, x must be greater than 30, so only x=33, y=10 and x=36, y=3 are eligible for the problem. Bringing the results of group 1 into the equation and calculating the number of days is less than 30, so the solution method is wrong, and the answer is the solution of group 2.
So worked for 3 days!
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Anonymous users2024-02-05Go to the bookstore and buy a copy, it's impossible not to have it!
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Anonymous users2024-02-04Go to the math network, it's amazing.
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I seem to know it, it doesn't seem to know me.