C) HCF of 900 and 243?

'highest common factor'

It is 9.

If you divide both by 9:

100, 27

100 and 27 have no more common factors

9

Step-by-step explanation:

This method uses only subtraction to find the HCF

• Subtract smaller number from larger number

• Repeat this until a common value is obtained

• The common value is the HCF

Given 900 and 243, then

900 - 243 = 657

657 - 243 = 414

414 - 243 = 171

243 - 171 = 72

171 - 72 = 99

99 - 72 = 27

72 - 27 = 45

45 - 27 = 18

27 - 18 = 9

18 - 9 = 9 ← common value of 9 obtained

Hence the HCF of 900 and 243 is 9