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Asking for help: two practical problems in sixth grade mathematics of primary school The first topic is: There are 18 spiders, dragonflies and cicadas, with 118 legs and 20 pairs of wings. It is known that spiders have 8 legs, dragonflies have 6 legs and 2 pairs of wings, and cicadas have 6 legs and 1 pair of wings?
Because spiders have no wings and the total number of legs of dragonflies and cicadas is equal, the condition of wings is discarded first
Set the question as
There are 18 spiders and 18 dragonflies with 118 legs. How many spiders and 6 dragonflies are there?
That makes it easier
Let's say it's all spiders
There are 8 * 18 = 144 legs, more than 144-118 = 26 legs
However, each spider has 8-6 more legs than dragonflies
So there are 26 / 2 = 13 dragonflies
There are 18-13 spiders = 5
The dragonfly and cicada are integrated because of the previous adaptation
So the 13 should be the total number of dragonflies and cicadas
Then we will face the second problem:
There are 13 dragonflies and 20 cicadas with two pairs of wings. How many of them are there?
Then we answer the question in the same way
Suppose there are all cicadas here, then there should be 1 * 13 = 13 pairs of wings
20-13 = 7 pairs less than it actually is
Each cicada has 2-1 fewer wings than dragonflies
So there are 7 / 1 = 7 dragonflies
There are 13-7 cicadas = 6
Finally, let's summarize
8*18=144
144-118=26
8-6=2
26/2=13
18-13=5
1*13=13
20-13=7
2-1=1
7/1=7
13-7=6
A: there are 5 spiders, 6 cicadas and 7 dragonflies
After the ice melts into water, the volume of water becomes 10 / 11 of that of ice. The volume of an existing piece of ice after melting into water is 30 cubic decimeters. What is the volume of this piece of ice? (formula calculation)
The maximum speed of a lion can reach 60 km / h, which is about 6 / 11 of that of a cheetah. What is the maximum speed of a cheetah
First question:
30/(10/11)=33
Second question:
60/(6/11)=110
Arithmetic, equation solution is unlimited, if good, the maximum election less additional 60
(in addition to the answer, please also indicate whether it is a question of encounter or pursuit. If neither of the two is true, then don't write it. In fact, if you can't write it, it doesn't matter. The key lies in the answer,
1. Xiao Ming's home is in the south of the school, and Xiao Fang's home is in the north of the school. The distance between the two families is 1410 meters. If Xiao Ming starts three minutes earlier than Xiao Fang, they can get to the school at the same time. It is known that Xiao Ming's speed is 70 meters / min, and Xiao Fang's speed is 50 meters / min. how many meters is Xiao Ming's home from the school?
2. The distance between station a and station B is 480 km. The express train goes from station a to station B at 5 a.m. and the local train goes from station B to station a at the same time. The two trains meet at 11 a.m. and after the express train arrives at station B at 3 p.m., how long does it take for the local train to continue driving to reach station a?
3. The distance between city a and city B is 138 kilometers. Zhang and Zhao set out from the two cities at the same time by bicycle and went opposite each other. Zhang's speed is 13 km / h, Zhao's speed is 12 km / h. Zhao was delayed for 1 hour due to car repair, and then went on to meet Zhang?
It's the highest reward, plus 60
The first problem is the encounter problem. If Xiaofang spends X minutes from home to school, then Xiaoming spends x + 3 minutes: 50 * x + 70 * (x + 3) = 1410, and the solution is x = 1200 / 120 = 10. Therefore, the distance between Xiaoming's home and school is: 70 * (x + 3) = 910 meters. The second problem is also the encounter problem. If the speed of the local bus is x, there will be 6
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