Question 638291
an equilateral triangle with sides of length 1cm has a perimeter of {{{3 cm}}}

if the circle rolls along a straight line of length {{{3 cm}}} (without slipping), it would need to make {{{three}}} complete turns 

the perimeter of the triangle {{{also}}} makes another turn (sum of external angles = 360), so the {{{circle}}} will need to make {{{4}}} turns in all