Answer:
25 cm
Explanation:
You want to know the length of the hypotenuse in a right triangle with legs 15 cm and 20 cm.
Pythagorean triple
The given leg lengths have the ratio ...
15 : 20 = 3 : 4 . . . . . . . scale factor of 5
This means they are part of a 3 : 4 : 5 right triangle.
The length "t cm" is 5·5 cm = 25 cm.
The value of t is 25.
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Additional comment
In case you've never heard of a {3, 4, 5} right triangle, you can figure the missing hypotenuse from the Pythagorean theorem:
c² = a² +b²
t² = 15² +20² = 225 +400 = 625
t = √625 = 25
The {3, 4, 5} Pythagorean triple is used repeatedly in algebra, geometry, and trig problems, along with some others: {5, 12, 13}, {7, 24, 25}, {8, 15, 17}. These can appear as multiples of the basic triple, as here, where the multiple is 5 × {3, 4, 5} = {15, 20, 25}.