2. There are red, yellow and blue 10 balls in one pocket. To touch the balls of the same color at a time, touch at least () balls at a time.
3. There are the following two sets of figures:
Group A: 1, 3, 5, 7, 9,1,13, 15, 17, 19.
Group B: 2,4,6,8, 10, 12, 14, 16,18,20.
Every time a sum is added from group A and group B, there are () different results.
A garment worker can produce 4 coats or 7 pairs of trousers per person every day. A coat and a pair of trousers are a suit. At present, 66 workers produce, how many sets of clothes can you produce at most every day?
Xiao Wang has three stamp albums, one fifth of all stamps are in the first one, n divided by 8(N is a non-zero natural number) is in the second one, and the remaining 39 stamps are in the third one. How many stamps does Xiao Wang have?
6. Xiao Ming looked at his report card and predicted that if the next math test was 100, the total average score would be 9 1. If he gets 80 points in the next exam, the overall average score will be 86 points. How many times did Xiao Ming take the math statistics exam?
7. A number is multiplied by three quarters, and the careless Xiaoming takes three quarters as three quarters. What should be the correct answer?
Xiao Li and Xiao Wang went to the bookstore to buy the same book, but they didn't have enough money. Xiao Li sent 4.5 yuan and Xiao Wang sent 0.6 yuan, so he decided to buy one. This money is just enough. How much is this book?
1 Because one 10,7290 multiplied by three 9s exceeds 5038, it can be seen that the maximum number of these four numbers does not exceed10.
Suppose these four numbers are 10 at most, and the other three are 7, 8 and 9.
Multiply these four numbers to get 7×8×9× 10=5040.
If the biggest one of these four numbers is 9, then the other three are 6, 7 and 8.
Multiply these four numbers to get 6×7×8×9=3024.
So these four numbers should be 7, 8, 9, 10. The multiplication result should be 5040.
Take at least four balls at a time to ensure that the colors of the two balls are the same.
The number of group A is 2n- 1, and n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
The number of group B is 2t, and t is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
Then group A and group B each take a number, and the result is 2n- 1+2t.
The result only depends on n+t, so as long as we know how many different results there are in n+T, we can know how many different results there are in the original problem.
(1) When n= 1, if t is an arbitrary number, there are 10 results;
(2) When n=2, only when t= 10 can we get different results from (1);
(2) When n=3, only when t= 10 can we get different results from (1) and (2);
...........................
(10) When n= 10, only when t= 10 can we get different results from (1), (2) and (10).
Therefore * * * has 10+ 1×9= 19 different results.
4 it is necessary to set up X workers to produce coats.
4x=7×(66-x)
Then x=42.
Therefore, 4×42= 168 sets of clothes can be produced in one day.
I got X test scores, and now my average score is A. Yes.
(xa+ 100)/(x+ 1)= 9 1
(xa+80)/(x+ 1)=86
The two expressions are subtracted, and 20/(x+ 1)=5.
Then x=3 a=88
That is, the results of the existing three exams.
Suppose it has x stamps.
x/5+N/8+39=x
Simplified to 4x/5-N/8=39.
According to the meaning of the question, n is the ending of 8, 4x/5 is an even number, and 39 is an odd number. Then n is the odd tail of 8. Let N=(2t+ 1)×8 to get 4x/5-(2t+ 1)=39.
x=( 100+5t)/2
Then 5t is an even number, let t=2w, x=( 100+5×2w)/2=50+5w.
Therefore, * * has 50+5w stamps, w is 0, 1, 2, 3, 4, ......
At this time N=32w+8.
7 If the multiplicand is A, the result should be 4a/3, and you can get 2 points. If the answer is accepted, you can get reward points and 20 points.