grade
How many students are there at least?
Suppose there are at least x students in this grade, then from the meaning of the question, x- 1 is a multiple of 3, and so is it.
A multiple of 5
Is a multiple of 7. Note: x- 1 is a multiple of 3 and a multiple of 5. Is it easy to understand? It is a multiple of 7 because if there are 7 people in each row and the result is 6 people, then x- 1 is 7 people in each row and the result is 7 people, which means it is divisible. So x- 1 is a multiple of 3,5,7, so at least x- 1 is 3,5,7.
least common multiple
That is, 105 people, then x is at least 106.
A: There are at least 106 students in this grade.
At present, there are 500 kilograms of brine containing salt 10%. To increase its concentration to 20%, it is necessary to
salt
How many kilograms?
Suppose x kilograms of salt is needed,
500× 10%+x=(500+x)×20%
The solution is x=62.5.
A: You need to add 62.5 kilograms of salt.
Xiaoli was happy at once.
Interest in mathematics
I answered 20 questions in the knowledge contest. Get 8 points for answering a question correctly; Deduct 5 points for wrong answer. Xiaoli scored 134. What is the correct answer? Some mistakes
Solution: let Xiaoli face the X road.
8x-5(20-x)= 134
8x- 100+5x= 134
13x=234
x= 18
20- 18=2 channels
A: Xiaoli 18 is right.
Two ways to be wrong.
Xiaoli has just finished attending.
primary school
mathematical contest
Her ranking, age and test scores add up to 29 10. What's her score and ranking?
Put 29 10
Decomposition of quality factors
Prime factors are 2, 3, 5 and 97. After analysis, Xiaoli scored 97, ranking third. (2X5= 10 suits her.
Grade?Five
age