Consider right triangle with two congruent legs of 7 meters each and unknown hypotenuse.
By the Pythagorean theorem,
[tex]\text{Hypotenuse}^2=\text{First leg}^2+\text{Second leg}^2.[/tex]
Thus,
[tex]\text{Hypotenuse}^2=7^2+7^2=49+49=98,\\ \\\text{Hypotenuse}=\sqrt{98}\approx 10\ m.[/tex]
Answer: 10 m