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What other math problems does Hua have?
6. Two cups are filled with 40% and 10% salt solution respectively, and the mixed salt solution is 30% after being poured together. If 600g of 20% salt solution is added, the concentration will become 25%. Then the original 40% salt water grams.

7. One of Wang Chun, Chen Gang and Yin Hua did something bad. When Miss Li learned of this situation, the three of them said the following words respectively:

Chen: It wasn't me. Yin Hua didn't do it either.

Wang: I didn't do it. Chen Gang didn't do either.

Yin: I didn't do it. I don't know who did it.

When Miss Li asked, she realized that they all told a truth and a lie, and it was Chen Gang who did the bad thing.

8. two cars, a and b, start from a and b respectively, and the directions are opposite. At the time of departure, the speed ratio of Party A and Party B is 5: 4. After meeting,

The speed of A is reduced by 20%, and the speed of B is increased by 20%, so when A arrives at B, B is still 10 km away from A ... Then A and B are 900 km away.

9. Xiao Li and Xiao Zhang start to make the same kind of parts at the same time. Each person can make 1 part per minute, but Xiao Li has to make three parts.

Rest 1 minute, Xiao Zhang will rest every four parts 1.5 minutes. Now they have to complete the task of 300 parts together, which takes 183 minutes.

10, three people, A, B and C, go to buy books, the number of books bought by B is 3, and the number of books bought by C is 1, so three people will buy at least four books altogether.