Question

Cho 1 hình tam giác có độ dài dây 12,5cm. Nếu tăng độ dài đáy thêm 4cm thì hình tam giác đó tăng thêm 17,2cm2. Tính diện tích tam giác đã cho.

Answer 1

Chiều cao là:

17,2 x 2 : 4 = 8,6 (cm)

Diện tích hình tam giác là:

12,5 x 8,6 : 2 = 53,75 (cm²)

Đáp số: 53,75cm²

Answer 2

Chiều cao hinh tam giac la : 17,2 x 2 : 4 = 8,6 (cm)

Diện tích hinh tam giac la: 12,5 x 8,6 : 2 = 53,75 (cm2)

                                     Đáp số : 53,75 cm vuong

Answer 3

Độ dài đáy mới :

  12,5 + 4 = 16,5 ( cm )

\(ax4:2=17,5\left(cm^2\right)\)S_{tam giác} = \(\frac{axh}{2}\)

Ta có :

\(\frac{ax16,5}{2}-\frac{ax12,5}{2}=17,2\left(cm^2\right)\)

\(ax\left(16,5-12,5\right):2=17,5\left(cm^2\right)\)

\(ax4:2=17,5\left(cm^2\right)\)

\(ax2=17,5\left(cm^2\right)\)

a = 17,5 : 2 = 8,75 ( cm² )

Diện tích tam giác đã cho :

  8,75 x 12,5 : 2 = 54,6875 ( cm² )

Answer 4

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