The average of three numbers is 369. Find that three numbers, knowning that three numbers have: a 3 - digit number; a 2 – digit number and a 1 – digit number?

In a working day, the four groups planted 174 eucalyptus trees. Group 1 planted 16 trees more than group 2, group 3 planted 10 trees less than group 1, group 4 planted is equal to the number of trees group 2. How many eucalyptus trees did each group plant?

Average age of father, An and Hong is 19 years old, the father's age is 25 years more than the total age of An and Hong, Hong is 8 years less than An. How old is each person?

An is 12 years younger than Binh. In 1997, An’s age is $\frac{3}{7}$ Binh’s age. What is the age of An in 2000?

A few years ago, there are four Mondays and four Fridays in the month of January. On which day in that year was 1^st of January ?

The sum of a father’s age and his son’s age is 60. The father’s age was 3 times his son’s age eight years ago. How old are they now ?

Find the smallest natural number N consist of 9 digits is $N=\overline{abceghik}$ , such that $\overline{ab}\vdots 2;\overline{abc}\vdots 3;\overline{abc\text{d}}\vdots 4;\overline{abc\text{d}e}\vdots 5;\overline{abc\deg }\vdots 6;\overline{abc\deg h}\vdots 7;\overline{abc\deg hi}\vdots 8;N\vdots 9$?

A rectangular piece of land has the length is 64m and the width is 34m. They decrease by the length and increase by the width so that the piece of land is square, knowing that the area decreases to the length of 272 m² . Find the area more follow the width ? (m² )

Randy and Sam spend 12 hours to complete a science project. If Randy works alone on the same project for 16 hours and let Sam take over, Sam needs another 7 hours to complete it. How many hours does Sam spend to complete the science project alone ?

A number is added to 3. The sum is then multiplied by 5. When 8 is subtracted from the product, the result is 12. Find the number at first ?

The ratio of the number of yellow balls to the toal number of balls in a bag was 5:7 at first. 18 more yellow balls were put into the bag. The ratio of the number of yellow balls to the total number of balls became 2 : 1. How many balls were there altogether in the end ?

Find a number, such that if that number is divided by 7, the remainder is 4. If that number is divided by 9, the remainder is 8 and the quotient is decreased by 2 units ?

They plant tree around a rectangle garden, the length is 61 m, the width is 25 m less than the length. They open two doors in the middle of the length ( like the picture ) ,each door wide 1 m. How many trees do they plant, such that trees are planted at regular intervals of 15dm and two side of door have different stake ? )

Find the irreducible fraction $\frac{a}{b}$such that if the numerator is increased by 6 and the denominator is increased by 21, the value of the new fraction is no change ?

( Write the result as a/b )

A rectangle has the area is 135 m². The length is  $\frac{3}{5}$ the width. Find the perimeter of the rectangle? ( m )