Tổng của hai số thập phân là 13,26. Nếu ta gấp số thứ nhất lên 5 lần số thứ hai lên 2 lần thì ta được hai số mới có tổng 35,4. Tìm hai số đó là

Let's solve each problem step by step:

Câu 5:
We know that the circumference of a circle is given by the formula C = 2πr, where C is the circumference and r is the radius.
In this case, the wheel makes 1000 revolutions, so the distance it travels is equal to the circumference of the circle.
39250 m = 2πr
Dividing both sides by 2π, we get:
r = 39250 / (2π) ≈ 6244.89 m
The area of a circle is given by the formula A = πr^2, where A is the area and r is the radius.
Plugging in the value of r, we get:
A = π(6244.89)^2 ≈ 122522712.8 m^2

Câu 6:
Let's assume the two decimal numbers are x and y.
We are given that x + y = 16.26.
If we multiply x by 7 and y by 4, we get the new numbers 7x and 4y.
We are also given that 7x + 4y = 72.9.
We can solve these two equations simultaneously to find the values of x and y.
Multiplying the first equation by 7 and the second equation by 4, we get:
7x + 7y = 113.82
28x + 16y = 291.6
Subtracting the first equation from the second equation, we get:
21x + 9y = 177.78
Solving this equation along with the first equation, we find:
x = 5.22
y = 11.04

Câu 7:
Let's assume the lengths of the two bases of the trapezoid are x and y.
We are given that the area of the trapezoid is 360 m^2.
Using the formula for the area of a trapezoid, we get:
360 = (x + y) * h / 2
where h is the height of the trapezoid.
We are also given that if we increase the length of the smaller base by 3 m and the length of the larger base by 6 m, we get a new trapezoid with an area of 45 m^2.
Using the same formula for the new trapezoid, we get:
45 = (x + 3 + y + 6) * h / 2
Simplifying both equations, we get:
720 = (x + y) * h
90 = (x + 9 + y) * h
Dividing the second equation by the first equation, we get:
90/720 = (x + 9 + y) / (x + y)
1/8 = (x + 9 + y) / (x + y)
Cross multiplying, we get:
x + 9 + y = 8x + 8y
7x - 7y = -9
Solving this equation along with the first equation, we find:
x = 12
y = 9