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Two 7-year-old practical problems (solved by equation) 1. Xiaoming and Xiaoli run back to each other along the circular track at the same time. They meet each other every 15 seconds. It is known that Xiaoming runs a lap for 24 seconds, and Xiaoli runs a lap for how many seconds? 2. At present, the concentration of 5% Guozhen beverage is 200g. If the concentration is to be increased to 10%, how much Guozhen should be added to the beverage?
1. Set the length of the track as X meters, and it takes y seconds for Xiaoli to run a lap
x/15=x/24+x/y
We get y = 40
2. If you need to add x grams of fruit
(5%*200+x)/(200+x)=10%
The result is: x = 100 / 9
Two practical problems of equation
1. One fifth of the class planned to take part in the general cleaning, and two people took the initiative to take part in the temporary cleaning, so that the actual number of people participating in the general cleaning was the remaining one-third. How many people were planned to take part in the general cleaning?
2. Reading a book, I read one sixth of the whole book on the first day, 24 pages on the second day, and half more than the sum of the previous two days on the third day. At this time, I didn't read a quarter of the whole book. How many pages are there in the whole book?
We need to solve the equation
1. There are X students in the class,
1/5x+2=1/4x
X=40
2. Set X pages in the book,
(1/6x+24)*(1+1/2)+1/4x=x
x=72
(actually, it's not difficult)
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