Câu 1: Trang 127 - Toán tiếng anh lớp 5:Given right trapezoid ABCD (as shown in the figure) with AB = 4cm, DC = 5cm, AD = 3cm. Draw a segment connecting two points D and B to make two triangles ABD and BDC.Cho hình thang vuông ABCD (xem hình vẽ) c

Nguyễn Thị Thanh Lam

1. Area of triangle ABD:
Since triangle ABD is a right triangle, we can use the formula for the area of a triangle: 1/2 * base * height.
In this case, the base AB = 4cm and the height AD = 3cm.
Therefore, the area of triangle ABD = 1/2 * 4 * 3 = 6 cm².

2. Area of triangle BDC:
Similarly, the area of triangle BDC can be calculated using the same formula for the area of a triangle.
The base DC = 5cm and the height BD = 3cm (since BD is the perpendicular from B to DC).
Therefore, the area of triangle BDC = 1/2 * 5 * 3 = 7.5 cm².

3. Percentage of the area of triangle ABD compared to that of triangle BDC:
To find the percentage, we need to calculate the ratio of the area of triangle ABD to the area of triangle BDC and then multiply by 100.
The ratio of the areas is 6/7.5 = 0.8.
Therefore, the percentage is 0.8 * 100 = 80%.
Hence, the area of triangle ABD is 80% of the area of triangle BDC.

4. Another way to find the area of triangle ABD:
Since triangle ABD is a right triangle, another way to calculate its area is by using the Pythagorean theorem.
We have AB = 4cm, AD = 3cm, and BD as the unknown hypotenuse of the triangle.
Using the Pythagorean theorem, we get BD = √(AB² + AD²) = √(4² + 3²) = √(16 + 9) = √25 = 5cm.
Now we can use the formula for the area of a triangle: 1/2 * base * height.
Therefore, the area of triangle ABD = 1/2 * 4 * 3 = 6 cm².

5. Another way to find the area of triangle BDC:
Similarly, we can use the Pythagorean theorem to find the length of BD in triangle BDC.
With DC = 5cm and BC as the unknown hypotenuse, we have BC = √(BD² + DC²) = √(3² + 5²) = √(9 + 25) = √34 cm.
Now, using the formula for the area of a triangle, we get: 1/2 * 5 * 3 = 7.5 cm².

6. Finally, we can compare the two areas and find the percentage as mentioned earlier:
Area of triangle ABD = 6 cm².
Area of triangle BDC = 7.5 cm².
Ratio of the areas = 6/7.5 = 0.8.
Percentage = 0.8 * 100 = 80%.
Therefore, the area of triangle ABD is 80% of the area of triangle BDC.

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Câu 1: Trang 127 - Toán tiếng anh lớp 5:Given right trapezoid ABCD (as shown in the figure) with AB...