Helen draws a random circle.
She then measures its diameter and circumference.
She gets a circumference, C, of 405 mm correct to 3 significant figures.
She gets a diameter, d, of 130 mm correct to 2 significant figures.
Helen wants to find the value of it using the formula n =
1 =
Calculate the lower bound and upper bound for Helen's value of .
Give your answers correct to 3 decimal places.
