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:  A) 10 cm  B) 30 cm  C) 25 cm  D) 20 cm  E) 35 cm
Required length   = HCF of 800 cm, 420 cm, 1220 cm   = 20 cm   Answer: Option 20 cm
<result>D</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?