Question

What is the value of a? a = ?

Answer 1

Answer:

  a = 15

Step-by-step explanation:

The Pythagorean theorem applies:

  a² + 20² = 25²

  a² = 625 - 400 . . . . . subtract 20²

  a = √225 . . . . . . . . . . take the square root

  a = 15

_____

You might recognize that the given measures (20, 25) are in the ratio 4:5. There is only one right triangle with sides in that ratio: the 3:4:5 right triangle. That is, the unknown side (a) matches

  a : 20 : 25 = 3 : 4 : 5 . . . . numbers on the left are 5 times those on the right

  a = 5·3 = 15

Answer 2

The correct answer is 15.