Câu 9:
The average mass of a group of children is 47kg. If  of the number of children are girls and their average mass is 39kg. Find the average mass of the boys.
Answer: The average mass of the boys is kg
 

Câu 10:
A 6-digit number begins with the digit 8. The number is divisible by 9 and all digits of the number are different. What is the possible smallest value of this number?
Answer: 

A 6 digit number begins with the digit 8. The number is divisible by 9 and all digit of the number are different . What is the possible smallest value of this number ?MNPQ is the square that is made up of to identical rectangles and two square of area 9cm2 and 16cm2. The area of the square MNPQ is ?I have two digit in the decimal part.Iam greater than 75 but less than 80 . What least possible number am I ?

A 4-digits number is divisble by all of the numbers from 1 to 10 ưithout any remainder .

find the smallest possible value of the 4 - digit number 

The sum of 2018 and a 3-digit number is a square number. Find the smallest possible value of the 3- digit numbers

If F is a 4- digit number, divisible by 9,10 and 13 then the smallest value of F is.........

When a particular six-digit number is multiplied by 2, 3, 4, 5 and 6 respectively, each of the
products is still a six-digit number with the same digits as the original number but in a different
order. Find the original number.

Question 9:

I am a two –digit number. I have digit “0” in the ones place. When I am divided by 6, the quotient is 8 and has remainder. Who am I?

Answer:

Question 10:

The difference of a 3-digit number and the smallest 3-digit number is just before of the greatest even 2-digit number. The  3-digit number is

in a 4-digit number, the ones digit is the possible largest number, the hundreds digit is the smallest odd number and the tens digit is 1 more than the hundreds digit. The thousands digit is the sum of the hundreds and the tens digit. Find the number

:
In a 4-digit number, the ones digit is the possible largest number, the hundreds digit is the smallest odd number and the tens digit is 1 more than the hundreds digit. The thousands digit is the sum of the hundreds and the tens digit. Find the number.
Answer: The number is