Ellen mows her lawn every 4 days while Ivan, who lives next door, mows his lawn every 5 days. if they both their lawns on July 3, on what day should they both be mowing their lawns together? Show your work.

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  10

Step-by-step explanation:

The Pythagorean theorem tells you the relationships of sides in a right triangle is ...

  a² + b² = c² . . . . . . where 'a' and 'b' are the legs, and 'c' is the hypotenuse

  6² +8² = c²

  36 +64 = c² = 100

  c = √100 = 10

The length of the hypotenuse is 10.

Additional comment

The ratio of the leg lengths is 8/6 = 4/3. The only right triangle with legs in the ratio 4/3 has the relationship ...

  hypotenuse : long leg : short leg = 5 : 4 : 3

If you multiply these numbers by 2, you see they correspond to the side lengths in this triangle. Your familiarity with a 3-4-5 right triangle can let you write down the answer immediately.