In the image, if you mark the points like this:

What is the length of BF?

40 m

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30 m

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50 m

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20 m

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Solution

The correct option is A
40 m

Consider the $△ A D F$

Since $∠ A F D = 90^{\circ}$ , AD is the hypotenuse.

${A F}^{2} + {F D}^{2} = {A D}^{2}$

${A F}^{2} + 40^{2} = 50^{2}$

${A F}^{2} = 2500 - 1600 = 900$

AF = 30 m.

BF = AB - AF = 70 - 30 = 40 m.

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In the image, if you mark the points like this: What is the length of BF?

The correct option is A 40 m Consider the △ADF Since ∠AFD=90∘, AD is the hypotenuse. AF2+FD2=AD2 AF2+402=502 AF2=2500−1600=900 AF = 30 m. BF = AB - AF = 70 - 30 = 40 m.

In the image, if you mark the points like this:

What is the length of BF?

The correct option is A
40 m

Consider the $△ A D F$

Since $∠ A F D = 90^{\circ}$ , AD is the hypotenuse.

${A F}^{2} + {F D}^{2} = {A D}^{2}$

${A F}^{2} + 40^{2} = 50^{2}$

${A F}^{2} = 2500 - 1600 = 900$

AF = 30 m.

BF = AB - AF = 70 - 30 = 40 m.