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# 100 congruent triangles that each has an angle of 15°. how many triangles would need to make a pinwheel?

So theres 100 congruent triangles that each have a measure to 15°. How many of these triangles are needed to make a pinwheel

### 3 Answers by Expert Tutors

Ebenezer O. | Aerospace Engr & Air Traffic Control Grad For General Ed. TutoringAerospace Engr & Air Traffic Control Gra...
4.6 4.6 (13 lesson ratings) (13)
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The Pinwheel is complete Circle which means it equals 360°

If you're given 100 triangles with angles 15° each,

Find how many triangles would make the pinwheel "P"

P = angle of a circle / angle of given triangle.

P = 360° / 15°

P = 24

So 24 triangles would be needed.

It's better, IMHO, to leave a little for the student to do on his/her own.  Otherwise, we're just doing their homework for them.  I set it up below; the student had to finish.

Steve S. | Tutoring in Precalculus, Trig, and Differential CalculusTutoring in Precalculus, Trig, and Diffe...
5.0 5.0 (3 lesson ratings) (3)
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If each triangle was 15°-75°-90° and you ended up with a pinwheel like the last video here, http://www.wikihow.com/Make-a-Pinwheel, you would only need four triangles because it would be the 90° angles that had to add to 360°

Context and procedure matters.
Philip P. | Effective and Affordable Math TutorEffective and Affordable Math Tutor
4.9 4.9 (416 lesson ratings) (416)
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The pinwheel makes a complete circle of 360 degrees.

Place the vertex of the 15 degree angle of each triangle at the center of the pinwheel.  Each triangle then takes up 15 degrees of the 360 degrees.

Can you solve it now?