What is the greatest possible length which can be used to measure exactly the lengths 8 m, 4 m 20 cm and 12 m 20 cm?	Choose the correct choice from the following choices.
A) 20 cm	B) 23 cm	C) 25cm	D) 10 cm	E) 28 cm
Required length = HCF of 800 cm, 420 cm, 1220 cm = 20 cm   20 cmnswer is 20 cm
<result>A</result>
What is the greatest possible length which can be used to measure exactly the lengths 8 m, 4 m 20 cm and 12 m 20 cm?