Posted by Tim on .
Hat sizes are determined by measuring the circumference of one's head in either inches or centimeters. Use ratio and Proportion to complete the following table.
Hat Size:
6 and 7/8
Head Circumference (to the nearest 1/5 in):
21 and 3/5
Head Circumference (to the nearest cm) 55
Hat Size:
?
Head Circumference (to the nearest 1/5 in):
?
Head Circumference (to the nearest cm)
62
Make sure to keep the same denominator for Hat Size and Head Circumference (to the nearest 1/5 in)

Math 
Henry,
55/S = (21 3/5) / (6 7/8).
Divide 21 3/5 by 6 7/8:
55/S = 3.142/1
Solve for S
S = 55/3.142 = 17.5 cm = 6 4/5 in. = Size of hat.
C = 55 cm = (55/2.54) in = 21.6 in. =
21 3/5 in
62/S = (21 3/5) /(6 7/8)
S = 19.74 cm = (19.74/2.54) in =
7.8 in = 7 4/5 in.