This Fluency Activity is a part of the Lesson 11, Unit 4, Grade 4. This fluency exercise prepares students for unknown angle problems in Lesson 11. Project a number bond with a whole of 90. Fill in 9 for one of the parts. On your personal white boards, write the number bond, filling in the unknown part. Draw a number bond with a whole of 90 and with 9 and 81 as parts.