Question

find the circumference of the diameter 4.2​

Answer 1

circumference = 2πr

circumference = 2×22/7×2.1 (because diameter = 2radius)

circumference = 2×22×0.3

circumference = 13.2cm²

here is your answer

Answer 2

diameter = 4•2 m

then,

radius = 2•1 m

$circumference \: of \: circle \: = 2\pi \times r$

= 2×22/7×2•1 m

= 2×22×0•3 m

= 13•2 m

hope this helps you.